refactor: refresh test suite to be modernised (#7489)

* chore: port karma tests

* chore: port karma tests

* chore: port karma tests

* chore: tests

* chore: tests

* chore: tests

* chore: fix issues with port collisions

* refactor: utils tests

* refactor: utils tests

* refactor: utils tests

* refactor: tests to vitests

* refactor: tests to vitests

* refactor: tests to vitests

* refactor: tests to vitests

* refactor: tests to vitests

* refactor: tests to vitests

* refactor: tests to vitests

* refactor: ci

* chore: install pw deps

* chore: fixx ai feedback

* chore: wip compatability tests

* chore: wip compatability tests

* chore: wip compatability tests

* refactor: wip smoke

* chore: smoke test run

* chore: update unzip

* chore: update testing

* chore: update testing

* chore: update testing

* chore: update testing

* chore: update testing

* chore: skip tests that cannot run on node 16 and lower

* chore: fix 16x under tests

* chore: rest of tests

* fix: functions and runs

* feat: added tests for esm smoke

* feat: added smoke

* chore: ignore ai gen plans

* chore: ci fixes

* chore: fix small p2s

.github/workflows/run-ci.yml

@@ -15,12 +15,43 @@ concurrency:
 jobs:
   ci:
     runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v6
+        with:
+          persist-credentials: true
+      - name: Setup node
+        uses: actions/setup-node@v6
+        with:
+          node-version: 24.x
+          cache: npm
+      - name: Install dependencies
+        run: npm ci
+      - name: Build project
+        run: npm run build
+      - name: Install Playwright with deps
+        run: npx playwright install --with-deps
+      - name: Run unit tests
+        run: npm run test:vitest:unit
+      - name: Run browser tests
+        run: npm run test:vitest:browser:headless
+      - name: Dependency Review
+        uses: actions/dependency-review-action@v4
+      - name: Upload build artifact
+        uses: actions/upload-artifact@v7
+        with:
+          name: axios
+          path: dist
+          retention-days: 1
 
+  cjs-smoke-tests:
+    name: CJS smoke tests (Node ${{ matrix.node-version }})
+    needs: ci
+    runs-on: ubuntu-latest
     strategy:
-      matrix:
-        node-version: [14.x, 16.x, 18.x, 20.x, 22.x, 24.x]
       fail-fast: false
-
+      matrix:
+        node-version: [12, 14, 16, 18]
     steps:
       - name: Checkout repo
         uses: actions/checkout@v6
@@ -31,21 +62,51 @@ jobs:
         with:
           node-version: ${{ matrix.node-version }}
           cache: npm
-      - name: Install dependencies Node 14
-        if: matrix.node-version == '14.x'
-        run: npm i
+          cache-dependency-path: tests/smoke/cjs/package-lock.json
       - name: Install dependencies
-        if: matrix.node-version != '14.x'
+        if: matrix.node-version == 16 || matrix.node-version == 18
         run: npm ci
-      - name: Build project
-        run: npm run build
-      - name: Run unit tests
-        run: npm run test:node
-      - name: Run package tests
-        run: npm run test:package
-      - name: Run browser tests
-        run: npm run test:browser
-        if: matrix.node-version == '24.x'
-      - name: Dependency Review
-        uses: actions/dependency-review-action@v4
-        if: matrix.node-version == '24.x'
+      - name: Download build artifact
+        uses: actions/download-artifact@v8
+        with:
+          name: axios
+          path: dist
+      - name: Install CJS smoke test dependencies
+        working-directory: tests/smoke/cjs
+        run: npm install
+      - name: Run CJS smoke tests
+        working-directory: tests/smoke/cjs
+        run: npm run test:smoke:cjs:mocha
+
+  esm-smoke-tests:
+    name: ESM smoke tests (Node ${{ matrix.node-version }})
+    needs: ci
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        node-version: [20, 22, 24]
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v6
+        with:
+          persist-credentials: true
+      - name: Setup node
+        uses: actions/setup-node@v6
+        with:
+          node-version: ${{ matrix.node-version }}
+          cache: npm
+          cache-dependency-path: tests/smoke/esm/package-lock.json
+      - name: Install dependencies
+        run: npm ci
+      - name: Download build artifact
+        uses: actions/download-artifact@v8
+        with:
+          name: axios
+          path: dist
+      - name: Install ESM smoke test dependencies
+        working-directory: tests/smoke/esm
+        run: npm install
+      - name: Run ESM smoke tests
+        working-directory: tests/smoke/esm
+        run: npm run test:smoke:esm:vitest

.gitignore

@@ -13,4 +13,5 @@ backup/
 .npmrc
 .env
 dist/
-.vscode/
+.vscode/
+docs/

package.json

@@ -52,6 +52,7 @@
     "test:vitest": "vitest run",
     "test:vitest:unit": "vitest run --project unit",
     "test:vitest:browser": "vitest run --project browser",
+    "test:vitest:browser:headless": "vitest run --project browser-headless",
     "test:vitest:watch": "vitest",
     "test:package": "npm run test:eslint && npm run test:exports",
     "test:eslint": "node bin/ssl_hotfix.js eslint lib/**/*.js",

tests/browser/adapter.browser.test.js

@@ -0,0 +1,178 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import axios from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader() {}
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return '';
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+  }
+
+  respondWith({ status = 200, statusText = 'OK', responseText = '' } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = responseText;
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+
+  abort() {}
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const sleep = (ms = 0) => new Promise((resolve) => setTimeout(resolve, ms));
+
+const waitForRequest = async (timeoutMs = 1000) => {
+  const start = Date.now();
+
+  while (Date.now() - start < timeoutMs) {
+    const request = requests.at(-1);
+    if (request) {
+      return request;
+    }
+
+    await sleep(0);
+  }
+
+  throw new Error('Expected an XHR request to be sent');
+};
+
+describe('adapter (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+    axios.interceptors.request.handlers = [];
+    axios.interceptors.response.handlers = [];
+  });
+
+  it('should support custom adapter', async () => {
+    const responsePromise = axios('/foo', {
+      adapter(config) {
+        return new Promise((resolve) => {
+          const request = new XMLHttpRequest();
+          request.open('GET', '/bar');
+
+          request.onreadystatechange = function onReadyStateChange() {
+            resolve({
+              config,
+              request,
+            });
+          };
+
+          request.send(null);
+        });
+      },
+    });
+
+    const request = await waitForRequest();
+    expect(request.url).toBe('/bar');
+
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should execute adapter code synchronously', async () => {
+    let asyncFlag = false;
+
+    const responsePromise = axios('/foo', {
+      adapter(config) {
+        return new Promise((resolve) => {
+          const request = new XMLHttpRequest();
+          request.open('GET', '/bar');
+
+          request.onreadystatechange = function onReadyStateChange() {
+            resolve({
+              config,
+              request,
+            });
+          };
+
+          expect(asyncFlag).toBe(false);
+          request.send(null);
+        });
+      },
+    });
+
+    asyncFlag = true;
+
+    const request = await waitForRequest();
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should execute adapter code asynchronously when interceptor is present', async () => {
+    let asyncFlag = false;
+
+    axios.interceptors.request.use((config) => {
+      config.headers.async = 'async it!';
+      return config;
+    });
+
+    const responsePromise = axios('/foo', {
+      adapter(config) {
+        return new Promise((resolve) => {
+          const request = new XMLHttpRequest();
+          request.open('GET', '/bar');
+
+          request.onreadystatechange = function onReadyStateChange() {
+            resolve({
+              config,
+              request,
+            });
+          };
+
+          expect(asyncFlag).toBe(true);
+          request.send(null);
+        });
+      },
+    });
+
+    asyncFlag = true;
+
+    const request = await waitForRequest();
+    request.respondWith();
+    await responsePromise;
+  });
+});

tests/browser/basicAuth.browser.test.js

@@ -0,0 +1,136 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import axios from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = '';
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return this.responseHeaders;
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+  }
+
+  respondWith({ status = 200, statusText = 'OK', responseText = '', responseHeaders = '' } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = responseText;
+    this.responseHeaders = responseHeaders;
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+
+  abort() {}
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const startRequest = (...args) => {
+  const promise = axios(...args);
+  const request = requests.at(-1);
+
+  expect(request).toBeDefined();
+
+  return { request, promise };
+};
+
+const flushSuccess = async (request, promise) => {
+  request.respondWith({ status: 200 });
+  await promise;
+};
+
+describe('basicAuth (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+  });
+
+  it('should accept HTTP Basic auth with username/password', async () => {
+    const { request, promise } = startRequest('/foo', {
+      auth: {
+        username: 'Aladdin',
+        password: 'open sesame',
+      },
+    });
+
+    expect(request.requestHeaders.Authorization).toBe('Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should accept HTTP Basic auth credentials without the password parameter', async () => {
+    const { request, promise } = startRequest('/foo', {
+      auth: {
+        username: 'Aladdin',
+      },
+    });
+
+    expect(request.requestHeaders.Authorization).toBe('Basic QWxhZGRpbjo=');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should accept HTTP Basic auth credentials with non-Latin1 characters in password', async () => {
+    const { request, promise } = startRequest('/foo', {
+      auth: {
+        username: 'Aladdin',
+        password: 'open ßç£☃sesame',
+      },
+    });
+
+    expect(request.requestHeaders.Authorization).toBe('Basic QWxhZGRpbjpvcGVuIMOfw6fCo+KYg3Nlc2FtZQ==');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should fail to encode HTTP Basic auth credentials with non-Latin1 characters in username', async () => {
+    await expect(axios('/foo', {
+      auth: {
+        username: 'Aladßç£☃din',
+        password: 'open sesame',
+      },
+    })).rejects.toThrow(/character/i);
+  });
+});

tests/browser/cancel.browser.test.js

@@ -0,0 +1,173 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import axios from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = '';
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.onabort = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return this.responseHeaders;
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+  }
+
+  respondWith({ status = 200, statusText = 'OK', responseText = '', responseHeaders = '' } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = responseText;
+    this.responseHeaders = responseHeaders;
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+
+  abort() {
+    this.statusText = 'abort';
+    if (this.onabort) {
+      this.onabort();
+    }
+  }
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const waitForRequest = async (timeoutMs = 1000) => {
+  const start = Date.now();
+
+  while (Date.now() - start < timeoutMs) {
+    const request = requests.at(-1);
+    if (request) {
+      return request;
+    }
+
+    await Promise.resolve();
+  }
+
+  throw new Error('Expected an XHR request to be sent');
+};
+
+describe('cancel (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+  });
+
+  describe('when called before sending request', () => {
+    it('rejects Promise with a CanceledError object', async () => {
+      const source = axios.CancelToken.source();
+      source.cancel('Operation has been canceled.');
+
+      const error = await axios
+        .get('/foo', {
+          cancelToken: source.token,
+        })
+        .catch((thrown) => thrown);
+
+      expect(axios.isCancel(error)).toBe(true);
+      expect(error.message).toBe('Operation has been canceled.');
+      expect(requests).toHaveLength(0);
+    });
+  });
+
+  describe('when called after request has been sent', () => {
+    it('rejects Promise with a CanceledError object', async () => {
+      const source = axios.CancelToken.source();
+      const promise = axios.get('/foo/bar', {
+        cancelToken: source.token,
+      });
+
+      const request = await waitForRequest();
+
+      // Call cancel() after the request has been sent, but before response is received.
+      source.cancel('Operation has been canceled.');
+      request.respondWith({
+        status: 200,
+        responseText: 'OK',
+      });
+
+      const error = await promise.catch((thrown) => thrown);
+
+      expect(axios.isCancel(error)).toBe(true);
+      expect(error.message).toBe('Operation has been canceled.');
+    });
+
+    it('calls abort on request object', async () => {
+      const source = axios.CancelToken.source();
+      const promise = axios.get('/foo/bar', {
+        cancelToken: source.token,
+      });
+
+      const request = await waitForRequest();
+
+      // Call cancel() after the request has been sent, but before response is received.
+      source.cancel();
+
+      await promise.catch(() => undefined);
+
+      expect(request.statusText).toBe('abort');
+    });
+  });
+
+  it('supports cancellation using AbortController signal', async () => {
+    const controller = new AbortController();
+    const promise = axios.get('/foo/bar', {
+      signal: controller.signal,
+    });
+
+    const request = await waitForRequest();
+
+    // Call abort() after the request has been sent, but before response is received.
+    controller.abort();
+    setTimeout(() => {
+      request.respondWith({
+        status: 200,
+        responseText: 'OK',
+      });
+    }, 0);
+
+    const error = await promise.catch((thrown) => thrown);
+    expect(axios.isCancel(error)).toBe(true);
+  });
+});

tests/browser/cancelToken.browser.test.js

@@ -0,0 +1,90 @@
+import { describe, expect, it } from 'vitest';
+
+import CancelToken from '../../lib/cancel/CancelToken.js';
+import CanceledError from '../../lib/cancel/CanceledError.js';
+
+describe('CancelToken (vitest browser)', () => {
+  describe('constructor', () => {
+    it('throws when executor is not specified', () => {
+      expect(() => new CancelToken()).toThrowError(
+        new TypeError('executor must be a function.')
+      );
+    });
+
+    it('throws when executor is not a function', () => {
+      expect(() => new CancelToken(123)).toThrowError(
+        new TypeError('executor must be a function.')
+      );
+    });
+  });
+
+  describe('reason', () => {
+    it('returns a CanceledError if cancellation has been requested', () => {
+      let cancel;
+      const token = new CancelToken((c) => {
+        cancel = c;
+      });
+
+      cancel('Operation has been canceled.');
+
+      expect(token.reason).toBeInstanceOf(CanceledError);
+      expect(token.reason?.message).toBe('Operation has been canceled.');
+    });
+
+    it('returns undefined if cancellation has not been requested', () => {
+      const token = new CancelToken(() => {});
+
+      expect(token.reason).toBeUndefined();
+    });
+  });
+
+  describe('promise', () => {
+    it('resolves when cancellation is requested', async () => {
+      let cancel;
+      const token = new CancelToken((c) => {
+        cancel = c;
+      });
+
+      cancel('Operation has been canceled.');
+      const reason = await token.promise;
+
+      expect(reason).toBeInstanceOf(CanceledError);
+      expect(reason.message).toBe('Operation has been canceled.');
+    });
+  });
+
+  describe('throwIfRequested', () => {
+    it('throws if cancellation has been requested', () => {
+      let cancel;
+      const token = new CancelToken((c) => {
+        cancel = c;
+      });
+
+      cancel('Operation has been canceled.');
+
+      expect(() => token.throwIfRequested()).toThrow(CanceledError);
+      expect(() => token.throwIfRequested()).toThrow('Operation has been canceled.');
+    });
+
+    it('does not throw if cancellation has not been requested', () => {
+      const token = new CancelToken(() => {});
+
+      expect(() => token.throwIfRequested()).not.toThrow();
+    });
+  });
+
+  describe('source', () => {
+    it('returns an object containing token and cancel function', () => {
+      const source = CancelToken.source();
+
+      expect(source.token).toBeInstanceOf(CancelToken);
+      expect(source.cancel).toBeTypeOf('function');
+      expect(source.token.reason).toBeUndefined();
+
+      source.cancel('Operation has been canceled.');
+
+      expect(source.token.reason).toBeInstanceOf(CanceledError);
+      expect(source.token.reason?.message).toBe('Operation has been canceled.');
+    });
+  });
+});

tests/browser/cookies.browser.test.js

@@ -0,0 +1,56 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import cookies from '../../lib/helpers/cookies.js';
+
+const clearAllCookies = () => {
+  const expiry = new Date(Date.now() - 86400000).toUTCString();
+
+  for (const cookie of document.cookie.split(';')) {
+    const name = cookie.split('=')[0].trim();
+
+    if (!name) {
+      continue;
+    }
+
+    // Clear both default-path and root-path cookies for the same key.
+    document.cookie = `${name}=; expires=${expiry}`;
+    document.cookie = `${name}=; expires=${expiry}; path=/`;
+  }
+};
+
+describe('helpers::cookies (vitest browser)', () => {
+  beforeEach(() => {
+    clearAllCookies();
+  });
+
+  afterEach(() => {
+    clearAllCookies();
+  });
+
+  it('writes cookies', () => {
+    cookies.write('foo', 'baz');
+
+    expect(document.cookie).toBe('foo=baz');
+  });
+
+  it('reads cookies', () => {
+    cookies.write('foo', 'abc');
+    cookies.write('bar', 'def');
+
+    expect(cookies.read('foo')).toBe('abc');
+    expect(cookies.read('bar')).toBe('def');
+  });
+
+  it('removes cookies', () => {
+    cookies.write('foo', 'bar');
+    cookies.remove('foo');
+
+    expect(cookies.read('foo')).toBeNull();
+  });
+
+  it('uri encodes values', () => {
+    cookies.write('foo', 'bar baz%');
+
+    expect(document.cookie).toBe('foo=bar%20baz%25');
+  });
+});

tests/browser/defaults.browser.test.js

@@ -0,0 +1,282 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import axios from '../../index.js';
+import defaults from '../../lib/defaults/index.js';
+import AxiosHeaders from '../../lib/core/AxiosHeaders.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = '';
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return this.responseHeaders;
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+  }
+
+  respondWith({ status = 200, statusText = 'OK', responseText = '', responseHeaders = '' } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = responseText;
+    this.responseHeaders = responseHeaders;
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+
+  abort() {}
+}
+
+const XSRF_COOKIE_NAME = 'CUSTOM-XSRF-TOKEN';
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const getLastRequest = () => {
+  const request = requests.at(-1);
+
+  expect(request).toBeDefined();
+
+  return request;
+};
+
+const finishRequest = async (request, promise) => {
+  request.respondWith({ status: 200 });
+  await promise;
+};
+
+describe('defaults (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+    delete axios.defaults.baseURL;
+    delete axios.defaults.headers.get['X-CUSTOM-HEADER'];
+    delete axios.defaults.headers.post['X-CUSTOM-HEADER'];
+    document.cookie = `${XSRF_COOKIE_NAME}=;expires=${new Date(Date.now() - 86400000).toUTCString()}`;
+  });
+
+  it('should transform request json', () => {
+    expect(defaults.transformRequest[0]({ foo: 'bar' }, new AxiosHeaders())).toBe('{"foo":"bar"}');
+  });
+
+  it("should also transform request json when 'Content-Type' is 'application/json'", () => {
+    const headers = new AxiosHeaders({
+      'Content-Type': 'application/json',
+    });
+
+    expect(defaults.transformRequest[0](JSON.stringify({ foo: 'bar' }), headers)).toBe('{"foo":"bar"}');
+    expect(defaults.transformRequest[0]([42, 43], headers)).toBe('[42,43]');
+    expect(defaults.transformRequest[0]('foo', headers)).toBe('"foo"');
+    expect(defaults.transformRequest[0](42, headers)).toBe('42');
+    expect(defaults.transformRequest[0](true, headers)).toBe('true');
+    expect(defaults.transformRequest[0](false, headers)).toBe('false');
+    expect(defaults.transformRequest[0](null, headers)).toBe('null');
+  });
+
+  it("should transform the plain data object to a FormData instance when header is 'multipart/form-data'", () => {
+    const headers = new AxiosHeaders({
+      'Content-Type': 'multipart/form-data',
+    });
+
+    const transformed = defaults.transformRequest[0]({ x: 1 }, headers);
+
+    expect(transformed).toBeInstanceOf(FormData);
+  });
+
+  it('should do nothing to request string', () => {
+    expect(defaults.transformRequest[0]('foo=bar', new AxiosHeaders())).toBe('foo=bar');
+  });
+
+  it('should transform response json', () => {
+    const data = defaults.transformResponse[0].call(defaults, '{"foo":"bar"}');
+
+    expect(typeof data).toBe('object');
+    expect(data.foo).toBe('bar');
+  });
+
+  it('should do nothing to response string', () => {
+    expect(defaults.transformResponse[0]('foo=bar')).toBe('foo=bar');
+  });
+
+  it('should use global defaults config', async () => {
+    const promise = axios('/foo');
+    const request = getLastRequest();
+
+    expect(request.url).toBe('/foo');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should use modified defaults config', async () => {
+    axios.defaults.baseURL = 'http://example.com/';
+
+    const promise = axios('/foo');
+    const request = getLastRequest();
+
+    expect(request.url).toBe('http://example.com/foo');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should use request config', async () => {
+    const promise = axios('/foo', {
+      baseURL: 'http://www.example.com',
+    });
+    const request = getLastRequest();
+
+    expect(request.url).toBe('http://www.example.com/foo');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should use default config for custom instance', async () => {
+    const instance = axios.create({
+      xsrfCookieName: XSRF_COOKIE_NAME,
+      xsrfHeaderName: 'X-CUSTOM-XSRF-TOKEN',
+    });
+    document.cookie = `${instance.defaults.xsrfCookieName}=foobarbaz`;
+
+    const promise = instance.get('/foo');
+    const request = getLastRequest();
+
+    expect(request.requestHeaders[instance.defaults.xsrfHeaderName]).toBe('foobarbaz');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should use GET headers', async () => {
+    axios.defaults.headers.get['X-CUSTOM-HEADER'] = 'foo';
+
+    const promise = axios.get('/foo');
+    const request = getLastRequest();
+
+    expect(request.requestHeaders['X-CUSTOM-HEADER']).toBe('foo');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should use POST headers', async () => {
+    axios.defaults.headers.post['X-CUSTOM-HEADER'] = 'foo';
+
+    const promise = axios.post('/foo', {});
+    const request = getLastRequest();
+
+    expect(request.requestHeaders['X-CUSTOM-HEADER']).toBe('foo');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should use header config', async () => {
+    const instance = axios.create({
+      headers: {
+        common: {
+          'X-COMMON-HEADER': 'commonHeaderValue',
+        },
+        get: {
+          'X-GET-HEADER': 'getHeaderValue',
+        },
+        post: {
+          'X-POST-HEADER': 'postHeaderValue',
+        },
+      },
+    });
+
+    const promise = instance.get('/foo', {
+      headers: {
+        'X-FOO-HEADER': 'fooHeaderValue',
+        'X-BAR-HEADER': 'barHeaderValue',
+      },
+    });
+    const request = getLastRequest();
+
+    expect(request.requestHeaders).toEqual(
+      AxiosHeaders.concat(defaults.headers.common, defaults.headers.get, {
+        'X-COMMON-HEADER': 'commonHeaderValue',
+        'X-GET-HEADER': 'getHeaderValue',
+        'X-FOO-HEADER': 'fooHeaderValue',
+        'X-BAR-HEADER': 'barHeaderValue',
+      }).toJSON()
+    );
+
+    await finishRequest(request, promise);
+  });
+
+  it('should be used by custom instance if set before instance created', async () => {
+    axios.defaults.baseURL = 'http://example.org/';
+    const instance = axios.create();
+
+    const promise = instance.get('/foo');
+    const request = getLastRequest();
+
+    expect(request.url).toBe('http://example.org/foo');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should not be used by custom instance if set after instance created', async () => {
+    const instance = axios.create();
+    axios.defaults.baseURL = 'http://example.org/';
+
+    const promise = instance.get('/foo/users');
+    const request = getLastRequest();
+
+    expect(request.url).toBe('/foo/users');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should resistant to ReDoS attack', async () => {
+    const instance = axios.create();
+    const start = performance.now();
+    const slashes = '/'.repeat(100000);
+    instance.defaults.baseURL = `/${slashes}bar/`;
+
+    const promise = instance.get('/foo');
+    const request = getLastRequest();
+    const elapsedTimeMs = performance.now() - start;
+
+    expect(elapsedTimeMs).toBeLessThan(20);
+    expect(request.url).toBe(`/${slashes}bar/foo`);
+
+    await finishRequest(request, promise);
+  });
+});

tests/browser/formdata.browser.test.js

@@ -0,0 +1,104 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import axios from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = '';
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return this.responseHeaders;
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+  }
+
+  respondWith({ status = 200, statusText = 'OK', responseText = '', responseHeaders = '' } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = responseText;
+    this.responseHeaders = responseHeaders;
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+
+  abort() {}
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const getLastRequest = () => {
+  const request = requests.at(-1);
+
+  expect(request).toBeDefined();
+
+  return request;
+};
+
+describe('formdata (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+  });
+
+  it('should allow FormData posting', async () => {
+    const responsePromise = axios.postForm('/foo', {
+      a: 'foo',
+      b: 'bar',
+    });
+    const request = getLastRequest();
+
+    expect(request.params).toBeInstanceOf(FormData);
+    expect(Object.fromEntries(request.params.entries())).toEqual({
+      a: 'foo',
+      b: 'bar',
+    });
+
+    request.respondWith({
+      status: 200,
+      responseText: '{}',
+      responseHeaders: 'Content-Type: application/json',
+    });
+    await responsePromise;
+  });
+});

tests/browser/headers.browser.test.js

@@ -0,0 +1,228 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import axios, { AxiosHeaders } from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return '';
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+  }
+
+  respondWith({ status = 200, statusText = 'OK', responseText = '' } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = responseText;
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+
+  abort() {}
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const getLastRequest = () => {
+  const request = requests.at(-1);
+
+  expect(request).toBeDefined();
+
+  return request;
+};
+
+const finishRequest = async (request, promise) => {
+  request.respondWith({ status: 200 });
+  await promise;
+};
+
+function testHeaderValue(headers, key, val) {
+  let found = false;
+
+  for (const k in headers) {
+    if (k.toLowerCase() === key.toLowerCase()) {
+      found = true;
+      expect(headers[k]).toBe(val);
+      break;
+    }
+  }
+
+  if (!found) {
+    if (typeof val === 'undefined') {
+      expect(Object.prototype.hasOwnProperty.call(headers, key)).toBe(false);
+    } else {
+      throw new Error(`${key} was not found in headers`);
+    }
+  }
+}
+
+describe('headers (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+  });
+
+  it('should default common headers', async () => {
+    const headers = axios.defaults.headers.common;
+    const promise = axios('/foo');
+    const request = getLastRequest();
+
+    for (const key in headers) {
+      if (Object.prototype.hasOwnProperty.call(headers, key)) {
+        expect(request.requestHeaders[key]).toBe(headers[key]);
+      }
+    }
+
+    await finishRequest(request, promise);
+  });
+
+  it('should respect common Content-Type header', async () => {
+    const instance = axios.create();
+    instance.defaults.headers.common['Content-Type'] = 'application/custom';
+
+    const promise = instance.patch('/foo', '');
+    const request = getLastRequest();
+
+    expect(request.requestHeaders['Content-Type']).toBe('application/custom');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should add extra headers for post', async () => {
+    const headers = AxiosHeaders.from(axios.defaults.headers.common).toJSON();
+    const promise = axios.post('/foo', 'fizz=buzz');
+    const request = getLastRequest();
+
+    for (const key in headers) {
+      expect(request.requestHeaders[key]).toBe(headers[key]);
+    }
+
+    await finishRequest(request, promise);
+  });
+
+  it('should reset headers by null or explicit undefined', async () => {
+    const promise = axios.create({
+      headers: {
+        common: {
+          'x-header-a': 'a',
+          'x-header-b': 'b',
+          'x-header-c': 'c',
+        },
+      },
+    }).post(
+      '/foo',
+      { fizz: 'buzz' },
+      {
+        headers: {
+          'Content-Type': null,
+          'x-header-a': null,
+          'x-header-b': undefined,
+        },
+      }
+    );
+    const request = getLastRequest();
+
+    testHeaderValue(request.requestHeaders, 'Content-Type', undefined);
+    testHeaderValue(request.requestHeaders, 'x-header-a', undefined);
+    testHeaderValue(request.requestHeaders, 'x-header-b', undefined);
+    testHeaderValue(request.requestHeaders, 'x-header-c', 'c');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should use application/json when posting an object', async () => {
+    const promise = axios.post('/foo/bar', {
+      firstName: 'foo',
+      lastName: 'bar',
+    });
+    const request = getLastRequest();
+
+    testHeaderValue(request.requestHeaders, 'Content-Type', 'application/json');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should remove content-type if data is empty', async () => {
+    const promise = axios.post('/foo');
+    const request = getLastRequest();
+
+    testHeaderValue(request.requestHeaders, 'Content-Type', undefined);
+
+    await finishRequest(request, promise);
+  });
+
+  it('should preserve content-type if data is false', async () => {
+    const promise = axios.post('/foo', false);
+    const request = getLastRequest();
+
+    testHeaderValue(request.requestHeaders, 'Content-Type', 'application/x-www-form-urlencoded');
+
+    await finishRequest(request, promise);
+  });
+
+  it('should allow an AxiosHeaders instance to be used as the value of the headers option', async () => {
+    const instance = axios.create({
+      headers: new AxiosHeaders({
+        xFoo: 'foo',
+        xBar: 'bar',
+      }),
+    });
+
+    const promise = instance.get('/foo', {
+      headers: {
+        XFOO: 'foo2',
+        xBaz: 'baz',
+      },
+    });
+    const request = getLastRequest();
+
+    expect(request.requestHeaders.xFoo).toBe('foo2');
+    expect(request.requestHeaders.xBar).toBe('bar');
+    expect(request.requestHeaders.xBaz).toBe('baz');
+    expect(request.requestHeaders.XFOO).toBeUndefined();
+
+    await finishRequest(request, promise);
+  });
+});

tests/browser/instance.browser.test.js

@@ -0,0 +1,255 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import axios from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = '';
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return this.responseHeaders;
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+  }
+
+  respondWith({ status = 200, statusText = 'OK', responseText = '', responseHeaders = '' } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = responseText;
+    this.responseHeaders = responseHeaders;
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const getLastRequest = () => {
+  const request = requests.at(-1);
+
+  expect(request).toBeDefined();
+
+  return request;
+};
+
+const flushSuccess = async (request, promise) => {
+  request.respondWith({ status: 200 });
+  await promise;
+};
+
+const waitForRequest = async (timeoutMs = 1000) => {
+  const start = Date.now();
+
+  while (Date.now() - start < timeoutMs) {
+    const request = requests.at(-1);
+    if (request) {
+      return request;
+    }
+
+    await Promise.resolve();
+  }
+
+  throw new Error('Expected an XHR request to be sent');
+};
+
+describe('instance (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+  });
+
+  it('should have the same methods as default instance', () => {
+    const instance = axios.create();
+
+    for (const prop in axios) {
+      if (
+        [
+          'Axios',
+          'AxiosError',
+          'create',
+          'Cancel',
+          'CanceledError',
+          'CancelToken',
+          'isCancel',
+          'all',
+          'spread',
+          'getUri',
+          'isAxiosError',
+          'mergeConfig',
+          'getAdapter',
+          'VERSION',
+          'default',
+          'toFormData',
+          'formToJSON',
+          'AxiosHeaders',
+          'HttpStatusCode',
+        ].includes(prop)
+      ) {
+        continue;
+      }
+
+      expect(typeof instance[prop]).toBe(typeof axios[prop]);
+    }
+  });
+
+  it('should make an http request without verb helper', async () => {
+    const instance = axios.create();
+    const promise = instance('/foo');
+    const request = getLastRequest();
+
+    expect(request.url).toBe('/foo');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should make an http request with url instead of baseURL', async () => {
+    const instance = axios.create({
+      url: 'https://api.example.com',
+    });
+    const promise = instance('/foo');
+    const request = getLastRequest();
+
+    expect(request.url).toBe('/foo');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should make an http request', async () => {
+    const instance = axios.create();
+    const promise = instance.get('/foo');
+    const request = getLastRequest();
+
+    expect(request.url).toBe('/foo');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should use instance options', async () => {
+    const instance = axios.create({ timeout: 1000 });
+    const promise = instance.get('/foo');
+    const request = getLastRequest();
+
+    expect(request.timeout).toBe(1000);
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should have defaults.headers', () => {
+    const instance = axios.create({
+      baseURL: 'https://api.example.com',
+    });
+
+    expect(typeof instance.defaults.headers).toBe('object');
+    expect(typeof instance.defaults.headers.common).toBe('object');
+  });
+
+  it('should have interceptors on the instance', async () => {
+    const requestInterceptorId = axios.interceptors.request.use((config) => {
+      config.foo = true;
+      return config;
+    });
+
+    const instance = axios.create();
+    const instanceInterceptorId = instance.interceptors.request.use((config) => {
+      config.bar = true;
+      return config;
+    });
+
+    try {
+      const responsePromise = instance.get('/foo');
+      const request = await waitForRequest();
+
+      request.respondWith({
+        status: 200,
+      });
+
+      const response = await responsePromise;
+
+      expect(response.config.foo).toBeUndefined();
+      expect(response.config.bar).toBe(true);
+    } finally {
+      axios.interceptors.request.eject(requestInterceptorId);
+      instance.interceptors.request.eject(instanceInterceptorId);
+    }
+  });
+
+  it('should have getUri on the instance', () => {
+    const instance = axios.create({
+      baseURL: 'https://api.example.com',
+    });
+    const options = {
+      url: 'foo/bar',
+      params: {
+        name: 'axios',
+      },
+    };
+
+    expect(instance.getUri(options)).toBe('https://api.example.com/foo/bar?name=axios');
+  });
+
+  it('should correctly build url without baseURL', () => {
+    const instance = axios.create();
+    const options = {
+      url: 'foo/bar?foo=bar',
+      params: {
+        name: 'axios',
+      },
+    };
+
+    expect(instance.getUri(options)).toBe('foo/bar?foo=bar&name=axios');
+  });
+
+  it('should correctly discard url hash mark', () => {
+    const instance = axios.create();
+    const options = {
+      baseURL: 'https://api.example.com',
+      url: 'foo/bar?foo=bar#hash',
+      params: {
+        name: 'axios',
+      },
+    };
+
+    expect(instance.getUri(options)).toBe('https://api.example.com/foo/bar?foo=bar&name=axios');
+  });
+});

tests/browser/interceptors.browser.test.js

@@ -0,0 +1,745 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import axios from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = {};
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.responseURL = '';
+    this.timeout = 0;
+    this.withCredentials = false;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.onabort = null;
+    this.onerror = null;
+    this.ontimeout = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    if (typeof this.responseHeaders === 'string') {
+      return this.responseHeaders;
+    }
+
+    return Object.entries(this.responseHeaders)
+      .map(([key, value]) => `${key}: ${value}`)
+      .join('\n');
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+    this.readyState = 1;
+  }
+
+  respondWith({
+    status = 200,
+    statusText = 'OK',
+    responseText = '',
+    response = null,
+    responseHeaders = {},
+    headers = {},
+    responseURL = '',
+  } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = response === null ? responseText : response;
+    this.responseHeaders = Object.keys(headers).length ? headers : responseHeaders;
+    this.responseURL = responseURL;
+    this.readyState = 4;
+    this.finish();
+  }
+
+  responseTimeout() {
+    if (this.ontimeout) {
+      this.ontimeout();
+    }
+  }
+
+  failNetworkError(message = 'Network Error') {
+    if (this.onerror) {
+      this.onerror({ message });
+    }
+  }
+
+  abort() {
+    if (this.onabort) {
+      this.onabort();
+    }
+  }
+
+  finish() {
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const sleep = (ms = 0) => new Promise((resolve) => setTimeout(resolve, ms));
+
+const waitForRequest = async (timeoutMs = 1000) => {
+  const start = Date.now();
+
+  while (Date.now() - start < timeoutMs) {
+    const request = requests.at(-1);
+    if (request) {
+      return request;
+    }
+
+    await sleep(0);
+  }
+
+  throw new Error('Expected an XHR request to be sent');
+};
+
+describe('interceptors (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+    axios.interceptors.request.handlers = [];
+    axios.interceptors.response.handlers = [];
+    vi.restoreAllMocks();
+  });
+
+  it('should add a request interceptor (asynchronous by default)', async () => {
+    let asyncFlag = false;
+
+    axios.interceptors.request.use((config) => {
+      config.headers.test = 'added by interceptor';
+      expect(asyncFlag).toBe(true);
+      return config;
+    });
+
+    const responsePromise = axios('/foo');
+    asyncFlag = true;
+
+    const request = await waitForRequest();
+    expect(request.requestHeaders.test).toBe('added by interceptor');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should add a request interceptor (explicitly flagged as asynchronous)', async () => {
+    let asyncFlag = false;
+
+    axios.interceptors.request.use(
+      (config) => {
+        config.headers.test = 'added by interceptor';
+        expect(asyncFlag).toBe(true);
+        return config;
+      },
+      null,
+      { synchronous: false }
+    );
+
+    const responsePromise = axios('/foo');
+    asyncFlag = true;
+
+    const request = await waitForRequest();
+    expect(request.requestHeaders.test).toBe('added by interceptor');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should add a request interceptor that is executed synchronously when flag is provided', async () => {
+    let asyncFlag = false;
+
+    axios.interceptors.request.use(
+      (config) => {
+        config.headers.test = 'added by synchronous interceptor';
+        expect(asyncFlag).toBe(false);
+        return config;
+      },
+      null,
+      { synchronous: true }
+    );
+
+    const responsePromise = axios('/foo');
+    asyncFlag = true;
+
+    const request = await waitForRequest();
+    expect(request.requestHeaders.test).toBe('added by synchronous interceptor');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should execute asynchronously when not all interceptors are explicitly flagged as synchronous', async () => {
+    let asyncFlag = false;
+
+    axios.interceptors.request.use((config) => {
+      config.headers.foo = 'uh oh, async';
+      expect(asyncFlag).toBe(true);
+      return config;
+    });
+
+    axios.interceptors.request.use(
+      (config) => {
+        config.headers.test = 'added by synchronous interceptor';
+        expect(asyncFlag).toBe(true);
+        return config;
+      },
+      null,
+      { synchronous: true }
+    );
+
+    axios.interceptors.request.use((config) => {
+      config.headers.test = 'added by the async interceptor';
+      expect(asyncFlag).toBe(true);
+      return config;
+    });
+
+    const responsePromise = axios('/foo');
+    asyncFlag = true;
+
+    const request = await waitForRequest();
+    expect(request.requestHeaders.foo).toBe('uh oh, async');
+    expect(request.requestHeaders.test).toBe('added by synchronous interceptor');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should execute request interceptor in legacy order', async () => {
+    let sequence = '';
+
+    axios.interceptors.request.use((config) => {
+      sequence += '1';
+      return config;
+    });
+
+    axios.interceptors.request.use((config) => {
+      sequence += '2';
+      return config;
+    });
+
+    axios.interceptors.request.use((config) => {
+      sequence += '3';
+      return config;
+    });
+
+    const responsePromise = axios({ url: '/foo' });
+    const request = await waitForRequest();
+
+    expect(sequence).toBe('321');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should execute request interceptor in order', async () => {
+    let sequence = '';
+
+    axios.interceptors.request.use((config) => {
+      sequence += '1';
+      return config;
+    });
+
+    axios.interceptors.request.use((config) => {
+      sequence += '2';
+      return config;
+    });
+
+    axios.interceptors.request.use((config) => {
+      sequence += '3';
+      return config;
+    });
+
+    const responsePromise = axios({
+      url: '/foo',
+      transitional: {
+        legacyInterceptorReqResOrdering: false,
+      },
+    });
+    const request = await waitForRequest();
+
+    expect(sequence).toBe('123');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('runs the interceptor if runWhen function is provided and resolves to true', async () => {
+    const onGetCall = (config) => config.method === 'get';
+
+    axios.interceptors.request.use(
+      (config) => {
+        config.headers.test = 'special get headers';
+        return config;
+      },
+      null,
+      { runWhen: onGetCall }
+    );
+
+    const responsePromise = axios('/foo');
+    const request = await waitForRequest();
+
+    expect(request.requestHeaders.test).toBe('special get headers');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('does not run the interceptor if runWhen function is provided and resolves to false', async () => {
+    const onPostCall = (config) => config.method === 'post';
+
+    axios.interceptors.request.use(
+      (config) => {
+        config.headers.test = 'special get headers';
+        return config;
+      },
+      null,
+      { runWhen: onPostCall }
+    );
+
+    const responsePromise = axios('/foo');
+    const request = await waitForRequest();
+
+    expect(request.requestHeaders.test).toBeUndefined();
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('does not run async interceptor if runWhen resolves to false (and runs synchronously)', async () => {
+    let asyncFlag = false;
+    const onPostCall = (config) => config.method === 'post';
+
+    axios.interceptors.request.use(
+      (config) => {
+        config.headers.test = 'special get headers';
+        return config;
+      },
+      null,
+      { synchronous: false, runWhen: onPostCall }
+    );
+
+    axios.interceptors.request.use(
+      (config) => {
+        config.headers.sync = 'hello world';
+        expect(asyncFlag).toBe(false);
+        return config;
+      },
+      null,
+      { synchronous: true }
+    );
+
+    const responsePromise = axios('/foo');
+    asyncFlag = true;
+
+    const request = await waitForRequest();
+    expect(request.requestHeaders.test).toBeUndefined();
+    expect(request.requestHeaders.sync).toBe('hello world');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should call request onRejected when interceptor throws', async () => {
+    const rejectedSpy = vi.fn();
+    const error = new Error('deadly error');
+
+    axios.interceptors.request.use(
+      () => {
+        throw error;
+      },
+      rejectedSpy,
+      { synchronous: true }
+    );
+
+    const responsePromise = axios('/foo').catch(() => {});
+    const request = await waitForRequest();
+    request.respondWith();
+    await responsePromise;
+
+    expect(rejectedSpy).toHaveBeenCalledWith(error);
+  });
+
+  it('should add a request interceptor that returns a new config object', async () => {
+    axios.interceptors.request.use(() => ({
+      url: '/bar',
+      method: 'post',
+    }));
+
+    const responsePromise = axios('/foo');
+    const request = await waitForRequest();
+
+    expect(request.method).toBe('POST');
+    expect(request.url).toBe('/bar');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should add a request interceptor that returns a promise', async () => {
+    axios.interceptors.request.use((config) =>
+      new Promise((resolve) => {
+        setTimeout(() => {
+          config.headers.async = 'promise';
+          resolve(config);
+        }, 100);
+      })
+    );
+
+    const responsePromise = axios('/foo');
+    const request = await waitForRequest(1500);
+
+    expect(request.requestHeaders.async).toBe('promise');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should add multiple request interceptors', async () => {
+    axios.interceptors.request.use((config) => {
+      config.headers.test1 = '1';
+      return config;
+    });
+    axios.interceptors.request.use((config) => {
+      config.headers.test2 = '2';
+      return config;
+    });
+    axios.interceptors.request.use((config) => {
+      config.headers.test3 = '3';
+      return config;
+    });
+
+    const responsePromise = axios('/foo');
+    const request = await waitForRequest();
+
+    expect(request.requestHeaders.test1).toBe('1');
+    expect(request.requestHeaders.test2).toBe('2');
+    expect(request.requestHeaders.test3).toBe('3');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should add a response interceptor', async () => {
+    axios.interceptors.response.use((data) => {
+      data.data = `${data.data} - modified by interceptor`;
+      return data;
+    });
+
+    const responsePromise = axios('/foo');
+    const request = await waitForRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: 'OK',
+    });
+
+    const response = await responsePromise;
+    expect(response.data).toBe('OK - modified by interceptor');
+  });
+
+  it('should add a response interceptor when request interceptor is defined', async () => {
+    axios.interceptors.request.use((data) => data);
+
+    axios.interceptors.response.use((data) => {
+      data.data = `${data.data} - modified by interceptor`;
+      return data;
+    });
+
+    const responsePromise = axios('/foo');
+    const request = await waitForRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: 'OK',
+    });
+
+    const response = await responsePromise;
+    expect(response.data).toBe('OK - modified by interceptor');
+  });
+
+  it('should add a response interceptor that returns a new data object', async () => {
+    axios.interceptors.response.use(() => ({
+      data: 'stuff',
+    }));
+
+    const responsePromise = axios('/foo');
+    const request = await waitForRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: 'OK',
+    });
+
+    const response = await responsePromise;
+    expect(response.data).toBe('stuff');
+  });
+
+  it('should add a response interceptor that returns a promise', async () => {
+    axios.interceptors.response.use((data) =>
+      new Promise((resolve) => {
+        setTimeout(() => {
+          data.data = 'you have been promised!';
+          resolve(data);
+        }, 10);
+      })
+    );
+
+    const responsePromise = axios('/foo');
+    const request = await waitForRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: 'OK',
+    });
+
+    const response = await responsePromise;
+    expect(response.data).toBe('you have been promised!');
+  });
+
+  describe('given multiple response interceptors', () => {
+    const fireRequest = async () => {
+      const responsePromise = axios('/foo');
+      const request = await waitForRequest();
+
+      request.respondWith({
+        status: 200,
+        responseText: 'OK',
+      });
+
+      return responsePromise;
+    };
+
+    it('then each interceptor is executed', async () => {
+      const interceptor1 = vi.fn((response) => response);
+      const interceptor2 = vi.fn((response) => response);
+
+      axios.interceptors.response.use(interceptor1);
+      axios.interceptors.response.use(interceptor2);
+
+      await fireRequest();
+
+      expect(interceptor1).toHaveBeenCalled();
+      expect(interceptor2).toHaveBeenCalled();
+    });
+
+    it('then they are executed in the order they were added', async () => {
+      const interceptor1 = vi.fn((response) => response);
+      const interceptor2 = vi.fn((response) => response);
+
+      axios.interceptors.response.use(interceptor1);
+      axios.interceptors.response.use(interceptor2);
+
+      await fireRequest();
+
+      expect(interceptor1.mock.invocationCallOrder[0]).toBeLessThan(interceptor2.mock.invocationCallOrder[0]);
+    });
+
+    it("then only the last interceptor's result is returned", async () => {
+      axios.interceptors.response.use(() => 'response 1');
+      axios.interceptors.response.use(() => 'response 2');
+
+      const response = await fireRequest();
+      expect(response).toBe('response 2');
+    });
+
+    it("then every interceptor receives the result of its predecessor", async () => {
+      axios.interceptors.response.use(() => 'response 1');
+      axios.interceptors.response.use((response) => [response, 'response 2']);
+
+      const response = await fireRequest();
+      expect(response).toEqual(['response 1', 'response 2']);
+    });
+
+    describe('and when the fulfillment interceptor throws', () => {
+      const fireRequestCatch = async () => {
+        const responsePromise = axios('/foo').catch(() => {});
+        const request = await waitForRequest();
+
+        request.respondWith({
+          status: 200,
+          responseText: 'OK',
+        });
+
+        await responsePromise;
+      };
+
+      it('then the following fulfillment interceptor is not called', async () => {
+        axios.interceptors.response.use(() => {
+          throw new Error('throwing interceptor');
+        });
+
+        const interceptor2 = vi.fn((response) => response);
+        axios.interceptors.response.use(interceptor2);
+
+        await fireRequestCatch();
+        expect(interceptor2).not.toHaveBeenCalled();
+      });
+
+      it('then the following rejection interceptor is called', async () => {
+        axios.interceptors.response.use(() => {
+          throw new Error('throwing interceptor');
+        });
+
+        const rejectIntercept = vi.fn((error) => Promise.reject(error));
+        axios.interceptors.response.use(() => {}, rejectIntercept);
+
+        await fireRequestCatch();
+        expect(rejectIntercept).toHaveBeenCalled();
+      });
+
+      it('once caught, another following fulfillment interceptor is called again', async () => {
+        axios.interceptors.response.use(() => {
+          throw new Error('throwing interceptor');
+        });
+
+        axios.interceptors.response.use(
+          () => {},
+          () => 'recovered'
+        );
+
+        const interceptor3 = vi.fn((response) => response);
+        axios.interceptors.response.use(interceptor3);
+
+        await fireRequestCatch();
+        expect(interceptor3).toHaveBeenCalled();
+      });
+    });
+  });
+
+  it('should allow removing interceptors', async () => {
+    axios.interceptors.response.use((data) => {
+      data.data = `${data.data}1`;
+      return data;
+    });
+    const intercept = axios.interceptors.response.use((data) => {
+      data.data = `${data.data}2`;
+      return data;
+    });
+    axios.interceptors.response.use((data) => {
+      data.data = `${data.data}3`;
+      return data;
+    });
+
+    axios.interceptors.response.eject(intercept);
+
+    const responsePromise = axios('/foo');
+    const request = await waitForRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: 'OK',
+    });
+
+    const response = await responsePromise;
+    expect(response.data).toBe('OK13');
+  });
+
+  it('should remove async interceptor before making request and execute synchronously', async () => {
+    let asyncFlag = false;
+
+    const asyncIntercept = axios.interceptors.request.use(
+      (config) => {
+        config.headers.async = 'async it!';
+        return config;
+      },
+      null,
+      { synchronous: false }
+    );
+
+    axios.interceptors.request.use(
+      (config) => {
+        config.headers.sync = 'hello world';
+        expect(asyncFlag).toBe(false);
+        return config;
+      },
+      null,
+      { synchronous: true }
+    );
+
+    axios.interceptors.request.eject(asyncIntercept);
+
+    const responsePromise = axios('/foo');
+    asyncFlag = true;
+
+    const request = await waitForRequest();
+    expect(request.requestHeaders.async).toBeUndefined();
+    expect(request.requestHeaders.sync).toBe('hello world');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should execute interceptors before transformers', async () => {
+    axios.interceptors.request.use((config) => {
+      config.data.baz = 'qux';
+      return config;
+    });
+
+    const responsePromise = axios.post('/foo', {
+      foo: 'bar',
+    });
+
+    const request = await waitForRequest();
+    expect(request.params).toEqual('{"foo":"bar","baz":"qux"}');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should modify base URL in request interceptor', async () => {
+    const instance = axios.create({
+      baseURL: 'http://test.com/',
+    });
+
+    instance.interceptors.request.use((config) => {
+      config.baseURL = 'http://rebase.com/';
+      return config;
+    });
+
+    const responsePromise = instance.get('/foo');
+    const request = await waitForRequest();
+
+    expect(request.url).toBe('http://rebase.com/foo');
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should clear all request interceptors', () => {
+    const instance = axios.create({
+      baseURL: 'http://test.com/',
+    });
+
+    instance.interceptors.request.use((config) => config);
+    instance.interceptors.request.clear();
+
+    expect(instance.interceptors.request.handlers.length).toBe(0);
+  });
+
+  it('should clear all response interceptors', () => {
+    const instance = axios.create({
+      baseURL: 'http://test.com/',
+    });
+
+    instance.interceptors.response.use((config) => config);
+    instance.interceptors.response.clear();
+
+    expect(instance.interceptors.response.handlers.length).toBe(0);
+  });
+});

tests/browser/isURLSameOrigin.browser.test.js

@@ -0,0 +1,13 @@
+import { describe, expect, it } from 'vitest';
+
+import isURLSameOrigin from '../../lib/helpers/isURLSameOrigin.js';
+
+describe('helpers::isURLSameOrigin (vitest browser)', () => {
+  it('detects same origin', () => {
+    expect(isURLSameOrigin(window.location.href)).toBe(true);
+  });
+
+  it('detects different origin', () => {
+    expect(isURLSameOrigin('https://github.com/axios/axios')).toBe(false);
+  });
+});

tests/browser/options.browser.test.js

@@ -0,0 +1,220 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import axios from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = '';
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return this.responseHeaders;
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+  }
+
+  respondWith({ status = 200, statusText = 'OK', responseText = '', responseHeaders = '' } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = responseText;
+    this.responseHeaders = responseHeaders;
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const startRequest = (...args) => {
+  const promise = axios(...args);
+  const request = requests.at(-1);
+
+  expect(request).toBeDefined();
+
+  return { request, promise };
+};
+
+const flushSuccess = async (request, promise) => {
+  request.respondWith({ status: 200 });
+  await promise;
+};
+
+describe('options (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+    vi.restoreAllMocks();
+  });
+
+  it('should default method to get', async () => {
+    const { request, promise } = startRequest('/foo');
+
+    expect(request.method).toBe('GET');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should accept headers', async () => {
+    const { request, promise } = startRequest('/foo', {
+      headers: {
+        'X-Requested-With': 'XMLHttpRequest',
+      },
+    });
+
+    expect(request.requestHeaders['X-Requested-With']).toBe('XMLHttpRequest');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should accept params', async () => {
+    const { request, promise } = startRequest('/foo', {
+      params: {
+        foo: 123,
+        bar: 456,
+      },
+    });
+
+    expect(request.url).toBe('/foo?foo=123&bar=456');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should allow overriding default headers', async () => {
+    const { request, promise } = startRequest('/foo', {
+      headers: {
+        Accept: 'foo/bar',
+      },
+    });
+
+    expect(request.requestHeaders.Accept).toBe('foo/bar');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should accept base URL', async () => {
+    const instance = axios.create({
+      baseURL: 'http://test.com/',
+    });
+
+    const promise = instance.get('/foo');
+    const request = requests.at(-1);
+
+    expect(request).toBeDefined();
+    expect(request.url).toBe('http://test.com/foo');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should warn about baseUrl', async () => {
+    const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+    const instance = axios.create({
+      baseUrl: 'http://example.com/',
+    });
+
+    const promise = instance.get('/foo');
+    const request = requests.at(-1);
+
+    expect(request).toBeDefined();
+    expect(warnSpy).toHaveBeenCalledWith('baseUrl is likely a misspelling of baseURL');
+    expect(request.url).toBe('/foo');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should ignore base URL if request URL is absolute', async () => {
+    const instance = axios.create({
+      baseURL: 'http://someurl.com/',
+    });
+
+    const promise = instance.get('http://someotherurl.com/');
+    const request = requests.at(-1);
+
+    expect(request).toBeDefined();
+    expect(request.url).toBe('http://someotherurl.com/');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should combine the URLs if base url and request url exist and allowAbsoluteUrls is false', async () => {
+    const instance = axios.create({
+      baseURL: 'http://someurl.com/',
+      allowAbsoluteUrls: false,
+    });
+
+    const promise = instance.get('http://someotherurl.com/');
+    const request = requests.at(-1);
+
+    expect(request).toBeDefined();
+    expect(request.url).toBe('http://someurl.com/http://someotherurl.com/');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should change only the baseURL of the specified instance', () => {
+    const instance1 = axios.create();
+    const instance2 = axios.create();
+
+    instance1.defaults.baseURL = 'http://instance1.example.com/';
+
+    expect(instance2.defaults.baseURL).not.toBe('http://instance1.example.com/');
+  });
+
+  it('should change only the headers of the specified instance', () => {
+    const instance1 = axios.create();
+    const instance2 = axios.create();
+
+    instance1.defaults.headers.common.Authorization = 'faketoken';
+    instance2.defaults.headers.common.Authorization = 'differentfaketoken';
+
+    instance1.defaults.headers.common['Content-Type'] = 'application/xml';
+    instance2.defaults.headers.common['Content-Type'] = 'application/x-www-form-urlencoded';
+
+    expect(axios.defaults.headers.common.Authorization).toBeUndefined();
+    expect(instance1.defaults.headers.common.Authorization).toBe('faketoken');
+    expect(instance2.defaults.headers.common.Authorization).toBe('differentfaketoken');
+
+    expect(axios.defaults.headers.common['Content-Type']).toBeUndefined();
+    expect(instance1.defaults.headers.common['Content-Type']).toBe('application/xml');
+    expect(instance2.defaults.headers.common['Content-Type']).toBe('application/x-www-form-urlencoded');
+  });
+});

tests/browser/progress.browser.test.js

@@ -0,0 +1,230 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import axios from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = {};
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.timeout = 0;
+    this.withCredentials = false;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.onabort = null;
+    this.onerror = null;
+    this.ontimeout = null;
+    this._listeners = {};
+    this._uploadListeners = {};
+    this.upload = {
+      addEventListener: (type, listener) => {
+        this._uploadListeners[type] ||= [];
+        this._uploadListeners[type].push(listener);
+      },
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener(type, listener) {
+    this._listeners[type] ||= [];
+    this._listeners[type].push(listener);
+  }
+
+  getAllResponseHeaders() {
+    return Object.entries(this.responseHeaders)
+      .map(([key, value]) => `${key}: ${value}`)
+      .join('\n');
+  }
+
+  send(data) {
+    this.params = data;
+    this.readyState = 1;
+    requests.push(this);
+  }
+
+  getListenerCount(type, target = 'request') {
+    const listeners = target === 'upload' ? this._uploadListeners : this._listeners;
+    return listeners[type]?.length || 0;
+  }
+
+  emit(type, target = 'request', event = {}) {
+    const listeners = target === 'upload' ? this._uploadListeners : this._listeners;
+    (listeners[type] || []).forEach((listener) => listener(event));
+  }
+
+  respondWith({
+    status = 200,
+    statusText = 'OK',
+    responseText = '',
+    response = null,
+    headers = {},
+  } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = response;
+    this.responseHeaders = headers;
+    this.readyState = 4;
+
+    this.emit('progress', 'request', {
+      loaded: responseText.length,
+      total: responseText.length,
+      lengthComputable: true,
+    });
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const getLastRequest = () => {
+  const request = requests.at(-1);
+
+  expect(request).toBeDefined();
+
+  return request;
+};
+
+describe('progress (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+    vi.restoreAllMocks();
+  });
+
+  it('should add a download progress handler', async () => {
+    const progressSpy = vi.fn();
+    const responsePromise = axios('/foo', { onDownloadProgress: progressSpy });
+    const request = getLastRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: '{"foo": "bar"}',
+    });
+    await responsePromise;
+
+    expect(progressSpy).toHaveBeenCalled();
+  });
+
+  it('should add an upload progress handler', async () => {
+    const progressSpy = vi.fn();
+    const responsePromise = axios('/foo', { onUploadProgress: progressSpy });
+    const request = getLastRequest();
+
+    expect(request.getListenerCount('progress', 'upload')).toBe(1);
+
+    request.respondWith({
+      status: 200,
+      responseText: '{"foo": "bar"}',
+    });
+    await responsePromise;
+  });
+
+  it('should add both upload and download progress handlers', async () => {
+    const downloadProgressSpy = vi.fn();
+    const uploadProgressSpy = vi.fn();
+    const responsePromise = axios('/foo', {
+      onDownloadProgress: downloadProgressSpy,
+      onUploadProgress: uploadProgressSpy,
+    });
+    const request = getLastRequest();
+
+    expect(downloadProgressSpy).not.toHaveBeenCalled();
+    expect(request.getListenerCount('progress', 'request')).toBe(1);
+    expect(request.getListenerCount('progress', 'upload')).toBe(1);
+
+    request.respondWith({
+      status: 200,
+      responseText: '{"foo": "bar"}',
+    });
+    await responsePromise;
+
+    expect(downloadProgressSpy).toHaveBeenCalled();
+  });
+
+  it('should add a download progress handler from instance config', async () => {
+    const progressSpy = vi.fn();
+    const instance = axios.create({
+      onDownloadProgress: progressSpy,
+    });
+
+    const responsePromise = instance.get('/foo');
+    const request = getLastRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: '{"foo": "bar"}',
+    });
+    await responsePromise;
+
+    expect(progressSpy).toHaveBeenCalled();
+  });
+
+  it('should add an upload progress handler from instance config', async () => {
+    const progressSpy = vi.fn();
+    const instance = axios.create({
+      onUploadProgress: progressSpy,
+    });
+
+    const responsePromise = instance.get('/foo');
+    const request = getLastRequest();
+
+    expect(request.getListenerCount('progress', 'upload')).toBe(1);
+
+    request.respondWith({
+      status: 200,
+      responseText: '{"foo": "bar"}',
+    });
+    await responsePromise;
+  });
+
+  it('should add upload and download progress handlers from instance config', async () => {
+    const downloadProgressSpy = vi.fn();
+    const uploadProgressSpy = vi.fn();
+    const instance = axios.create({
+      onDownloadProgress: downloadProgressSpy,
+      onUploadProgress: uploadProgressSpy,
+    });
+
+    const responsePromise = instance.get('/foo');
+    const request = getLastRequest();
+
+    expect(downloadProgressSpy).not.toHaveBeenCalled();
+    expect(request.getListenerCount('progress', 'request')).toBe(1);
+    expect(request.getListenerCount('progress', 'upload')).toBe(1);
+
+    request.respondWith({
+      status: 200,
+      responseText: '{"foo": "bar"}',
+    });
+    await responsePromise;
+
+    expect(downloadProgressSpy).toHaveBeenCalled();
+  });
+});

tests/browser/promise.browser.test.js

@@ -0,0 +1,122 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import axios from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = '';
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return this.responseHeaders;
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+  }
+
+  respondWith({ status = 200, statusText = 'OK', responseText = '', responseHeaders = '' } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = responseText;
+    this.responseHeaders = responseHeaders;
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+
+  abort() {}
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const getLastRequest = () => {
+  const request = requests.at(-1);
+
+  expect(request).toBeDefined();
+
+  return request;
+};
+
+describe('promise (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+  });
+
+  it('should provide succinct object to then', async () => {
+    const responsePromise = axios('/foo');
+    const request = getLastRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: '{"hello":"world"}',
+      responseHeaders: 'Content-Type: application/json',
+    });
+
+    const response = await responsePromise;
+
+    expect(typeof response).toBe('object');
+    expect(response.data.hello).toBe('world');
+    expect(response.status).toBe(200);
+    expect(response.headers['content-type']).toBe('application/json');
+    expect(response.config.url).toBe('/foo');
+  });
+
+  it('should support all', async () => {
+    const result = await axios.all([true, 123]);
+
+    expect(result).toEqual([true, 123]);
+  });
+
+  it('should support spread', async () => {
+    let fulfilled = false;
+    const result = await axios.all([123, 456]).then(
+      axios.spread((a, b) => {
+        expect(a + b).toBe(123 + 456);
+        fulfilled = true;
+        return 'hello world';
+      })
+    );
+
+    expect(fulfilled).toBe(true);
+    expect(result).toBe('hello world');
+  });
+});

tests/browser/requests.browser.test.js

@@ -0,0 +1,497 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import axios from '../../index.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = {};
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.responseURL = '';
+    this.timeout = 0;
+    this.withCredentials = false;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.onabort = null;
+    this.onerror = null;
+    this.ontimeout = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return Object.entries(this.responseHeaders)
+      .map(([key, value]) => `${key}: ${value}`)
+      .join('\n');
+  }
+
+  send(data) {
+    this.params = data;
+    this.readyState = 1;
+    requests.push(this);
+  }
+
+  respondWith({
+    status = 200,
+    statusText = 'OK',
+    responseText = '',
+    response = null,
+    headers = {},
+    responseURL = '',
+  } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = response;
+    this.responseHeaders = headers;
+    this.responseURL = responseURL;
+    this.readyState = 4;
+    this.finish();
+  }
+
+  responseTimeout() {
+    if (this.ontimeout) {
+      this.ontimeout();
+    }
+  }
+
+  failNetworkError(message = 'Network Error') {
+    if (this.onerror) {
+      this.onerror({ message });
+    }
+  }
+
+  abort() {
+    if (this.onabort) {
+      this.onabort();
+    }
+  }
+
+  finish() {
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const startRequest = (...args) => {
+  const promise = axios(...args);
+  const request = requests.at(-1);
+  expect(request).toBeDefined();
+
+  return { request, promise };
+};
+
+const flushSuccess = async (request, promise) => {
+  request.respondWith({ status: 200 });
+  await promise;
+};
+
+describe('requests (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+    vi.restoreAllMocks();
+  });
+
+  it('should treat single string arg as url', async () => {
+    const { request, promise } = startRequest('/foo');
+
+    expect(request.url).toBe('/foo');
+    expect(request.method).toBe('GET');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should treat method value as lowercase string', async () => {
+    const { request, promise } = startRequest({
+      url: '/foo',
+      method: 'POST',
+    });
+
+    request.respondWith({ status: 200 });
+    const response = await promise;
+
+    expect(response.config.method).toBe('post');
+  });
+
+  it('should allow string arg as url, and config arg', async () => {
+    const { request, promise } = startRequest('/foo', {
+      method: 'post',
+    });
+
+    expect(request.url).toBe('/foo');
+    expect(request.method).toBe('POST');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should allow data', async () => {
+    const { request, promise } = startRequest('/foo', {
+      method: 'delete',
+      data: { foo: 'bar' },
+    });
+
+    expect(request.params).toBe(JSON.stringify({ foo: 'bar' }));
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should make an http request', async () => {
+    const { request, promise } = startRequest('/foo');
+
+    expect(request.url).toBe('/foo');
+
+    await flushSuccess(request, promise);
+  });
+
+  describe('timeouts', () => {
+    it('should handle timeouts', async () => {
+      const { request, promise } = startRequest({
+        url: '/foo',
+        timeout: 100,
+      });
+
+      request.responseTimeout();
+
+      const err = await promise.catch((error) => error);
+
+      expect(err).toBeInstanceOf(Error);
+      expect(err.code).toBe('ECONNABORTED');
+    });
+
+    describe('transitional.clarifyTimeoutError', () => {
+      it('should throw ETIMEDOUT instead of ECONNABORTED on request timeouts', async () => {
+        const { request, promise } = startRequest({
+          url: '/foo',
+          timeout: 100,
+          transitional: {
+            clarifyTimeoutError: true,
+          },
+        });
+
+        request.responseTimeout();
+
+        const err = await promise.catch((error) => error);
+
+        expect(err).toBeInstanceOf(Error);
+        expect(err.code).toBe('ETIMEDOUT');
+      });
+    });
+  });
+
+  it('should reject on network errors', async () => {
+    const { request, promise } = startRequest('http://thisisnotaserver/foo');
+
+    request.failNetworkError();
+
+    const reason = await promise.catch((error) => error);
+
+    expect(reason).toBeInstanceOf(Error);
+    expect(reason.config.method).toBe('get');
+    expect(reason.config.url).toBe('http://thisisnotaserver/foo');
+    expect(reason.request).toBeInstanceOf(MockXMLHttpRequest);
+  });
+
+  it('should reject on abort', async () => {
+    const { request, promise } = startRequest('/foo');
+
+    request.abort();
+
+    const reason = await promise.catch((error) => error);
+
+    expect(reason).toBeInstanceOf(Error);
+    expect(reason.config.method).toBe('get');
+    expect(reason.config.url).toBe('/foo');
+    expect(reason.request).toBeInstanceOf(MockXMLHttpRequest);
+  });
+
+  it('should reject when validateStatus returns false', async () => {
+    const { request, promise } = startRequest('/foo', {
+      validateStatus(status) {
+        return status !== 500;
+      },
+    });
+
+    request.respondWith({ status: 500 });
+    const reason = await promise.catch((error) => error);
+
+    expect(reason).toBeInstanceOf(Error);
+    expect(reason.message).toBe('Request failed with status code 500');
+    expect(reason.config.method).toBe('get');
+    expect(reason.config.url).toBe('/foo');
+    expect(reason.response.status).toBe(500);
+  });
+
+  it('should resolve when validateStatus returns true', async () => {
+    const { request, promise } = startRequest('/foo', {
+      validateStatus(status) {
+        return status === 500;
+      },
+    });
+
+    request.respondWith({ status: 500 });
+    await expect(promise).resolves.toBeDefined();
+  });
+
+  it('should resolve when the response status is 0 (file protocol)', async () => {
+    const { request, promise } = startRequest('file:///xxx');
+
+    request.respondWith({
+      status: 0,
+      responseURL: 'file:///xxx',
+    });
+
+    await expect(promise).resolves.toBeDefined();
+  });
+
+  it('should resolve when validateStatus is null', async () => {
+    const { request, promise } = startRequest('/foo', {
+      validateStatus: null,
+    });
+
+    request.respondWith({ status: 500 });
+    await expect(promise).resolves.toBeDefined();
+  });
+
+  it('should resolve when validateStatus is undefined', async () => {
+    const { request, promise } = startRequest('/foo', {
+      validateStatus: undefined,
+    });
+
+    request.respondWith({ status: 500 });
+    await expect(promise).resolves.toBeDefined();
+  });
+
+  // https://github.com/axios/axios/issues/378
+  it('should return JSON when rejecting', async () => {
+    const { request, promise } = startRequest(
+      '/api/account/signup',
+      {
+        username: null,
+        password: null,
+      },
+      {
+        method: 'post',
+        headers: {
+          Accept: 'application/json',
+        },
+      }
+    );
+
+    request.respondWith({
+      status: 400,
+      statusText: 'Bad Request',
+      responseText: '{"error": "BAD USERNAME", "code": 1}',
+    });
+
+    const error = await promise.catch((err) => err);
+    const response = error.response;
+
+    expect(typeof response.data).toBe('object');
+    expect(response.data.error).toBe('BAD USERNAME');
+    expect(response.data.code).toBe(1);
+  });
+
+  it('should make cross domain http request', async () => {
+    const { request, promise } = startRequest('www.someurl.com/foo', {
+      method: 'post',
+    });
+
+    request.respondWith({
+      status: 200,
+      statusText: 'OK',
+      responseText: '{"foo": "bar"}',
+      headers: {
+        'Content-Type': 'application/json',
+      },
+    });
+
+    const response = await promise;
+
+    expect(response.data.foo).toBe('bar');
+    expect(response.status).toBe(200);
+    expect(response.statusText).toBe('OK');
+    expect(response.headers['content-type']).toBe('application/json');
+  });
+
+  it('should supply correct response', async () => {
+    const { request, promise } = startRequest('/foo', {
+      method: 'post',
+    });
+
+    request.respondWith({
+      status: 200,
+      statusText: 'OK',
+      responseText: '{"foo": "bar"}',
+      headers: {
+        'Content-Type': 'application/json',
+      },
+    });
+
+    const response = await promise;
+
+    expect(response.data.foo).toBe('bar');
+    expect(response.status).toBe(200);
+    expect(response.statusText).toBe('OK');
+    expect(response.headers['content-type']).toBe('application/json');
+  });
+
+  it('should not modify the config url with relative baseURL', async () => {
+    const { request, promise } = startRequest('/foo', {
+      baseURL: '/api',
+    });
+
+    request.respondWith({
+      status: 404,
+      statusText: 'NOT FOUND',
+      responseText: 'Resource not found',
+    });
+
+    const error = await promise.catch((err) => err);
+    const config = error.config;
+
+    expect(config.baseURL).toBe('/api');
+    expect(config.url).toBe('/foo');
+  });
+
+  it('should allow overriding Content-Type header case-insensitive', async () => {
+    const contentType = 'application/vnd.myapp.type+json';
+    const { request, promise } = startRequest('/foo', {
+      method: 'post',
+      data: { prop: 'value' },
+      headers: {
+        'Content-Type': contentType,
+      },
+    });
+
+    expect(request.requestHeaders['Content-Type']).toBe(contentType);
+    await flushSuccess(request, promise);
+  });
+
+  it('should support binary data as array buffer', async () => {
+    const input = new Int8Array([1, 2]);
+    const { request, promise } = startRequest('/foo', {
+      method: 'post',
+      data: input.buffer,
+    });
+
+    const output = new Int8Array(request.params);
+    expect(output.length).toBe(2);
+    expect(output[0]).toBe(1);
+    expect(output[1]).toBe(2);
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should support binary data as array buffer view', async () => {
+    const input = new Int8Array([1, 2]);
+    const { request, promise } = startRequest('/foo', {
+      method: 'post',
+      data: input,
+    });
+
+    const output = new Int8Array(request.params);
+    expect(output.length).toBe(2);
+    expect(output[0]).toBe(1);
+    expect(output[1]).toBe(2);
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should support array buffer response', async () => {
+    const str2ab = (str) => {
+      const buff = new ArrayBuffer(str.length * 2);
+      const view = new Uint16Array(buff);
+
+      for (let i = 0; i < str.length; i++) {
+        view[i] = str.charCodeAt(i);
+      }
+
+      return buff;
+    };
+
+    const { request, promise } = startRequest('/foo', {
+      responseType: 'arraybuffer',
+    });
+
+    request.respondWith({
+      status: 200,
+      response: str2ab('Hello world'),
+    });
+
+    const response = await promise;
+    expect(response.data.byteLength).toBe(22);
+  });
+
+  it('should support URLSearchParams', async () => {
+    const params = new URLSearchParams();
+    params.append('param1', 'value1');
+    params.append('param2', 'value2');
+
+    const { request, promise } = startRequest('/foo', {
+      method: 'post',
+      data: params,
+    });
+
+    expect(request.requestHeaders['Content-Type']).toBe(
+      'application/x-www-form-urlencoded;charset=utf-8'
+    );
+    expect(request.params).toBe('param1=value1&param2=value2');
+
+    await flushSuccess(request, promise);
+  });
+
+  it('should support HTTP protocol', async () => {
+    const { request, promise } = startRequest('/foo', {
+      method: 'get',
+    });
+
+    expect(request.method).toBe('GET');
+    await flushSuccess(request, promise);
+  });
+
+  it('should support HTTPS protocol', async () => {
+    const { request, promise } = startRequest('https://www.google.com', {
+      method: 'get',
+    });
+
+    expect(request.method).toBe('GET');
+    await flushSuccess(request, promise);
+  });
+
+  it('should return unsupported protocol error message', async () => {
+    await expect(axios.get('ftp:localhost')).rejects.toMatchObject({
+      message: 'Unsupported protocol ftp:',
+    });
+  });
+});

tests/browser/settle.browser.test.js

@@ -0,0 +1,99 @@
+import { describe, expect, it, vi } from 'vitest';
+
+import settle from '../../lib/core/settle.js';
+import AxiosError from '../../lib/core/AxiosError.js';
+
+describe('core::settle (vitest browser)', () => {
+  it('resolves when response status is missing', () => {
+    const resolve = vi.fn();
+    const reject = vi.fn();
+    const response = {
+      config: {
+        validateStatus: () => true,
+      },
+    };
+
+    settle(resolve, reject, response);
+
+    expect(resolve).toHaveBeenCalledOnce();
+    expect(resolve).toHaveBeenCalledWith(response);
+    expect(reject).not.toHaveBeenCalled();
+  });
+
+  it('resolves when validateStatus is not configured', () => {
+    const resolve = vi.fn();
+    const reject = vi.fn();
+    const response = {
+      status: 500,
+      config: {},
+    };
+
+    settle(resolve, reject, response);
+
+    expect(resolve).toHaveBeenCalledOnce();
+    expect(resolve).toHaveBeenCalledWith(response);
+    expect(reject).not.toHaveBeenCalled();
+  });
+
+  it('resolves when validateStatus returns true', () => {
+    const resolve = vi.fn();
+    const reject = vi.fn();
+    const response = {
+      status: 500,
+      config: {
+        validateStatus: () => true,
+      },
+    };
+
+    settle(resolve, reject, response);
+
+    expect(resolve).toHaveBeenCalledOnce();
+    expect(resolve).toHaveBeenCalledWith(response);
+    expect(reject).not.toHaveBeenCalled();
+  });
+
+  it('rejects with an AxiosError when validateStatus returns false', () => {
+    const resolve = vi.fn();
+    const reject = vi.fn();
+    const request = {
+      path: '/foo',
+    };
+    const response = {
+      status: 500,
+      config: {
+        validateStatus: () => false,
+      },
+      request,
+    };
+
+    settle(resolve, reject, response);
+
+    expect(resolve).not.toHaveBeenCalled();
+    expect(reject).toHaveBeenCalledOnce();
+
+    const reason = reject.mock.calls[0][0];
+    expect(reason).toBeInstanceOf(AxiosError);
+    expect(reason.message).toBe('Request failed with status code 500');
+    expect(reason.code).toBe(AxiosError.ERR_BAD_RESPONSE);
+    expect(reason.config).toBe(response.config);
+    expect(reason.request).toBe(request);
+    expect(reason.response).toBe(response);
+  });
+
+  it('passes response status to validateStatus', () => {
+    const resolve = vi.fn();
+    const reject = vi.fn();
+    const validateStatus = vi.fn();
+    const response = {
+      status: 500,
+      config: {
+        validateStatus,
+      },
+    };
+
+    settle(resolve, reject, response);
+
+    expect(validateStatus).toHaveBeenCalledOnce();
+    expect(validateStatus).toHaveBeenCalledWith(500);
+  });
+});

tests/browser/smoke.browser.test.js

@@ -1,10 +0,0 @@
-import { expect, test } from 'vitest';
-
-test('runs in browser environment', () => {
-  document.body.innerHTML = '<div data-testid="smoke">vitest browser smoke</div>';
-
-  const el = document.querySelector('[data-testid="smoke"]');
-
-  expect(el?.textContent).toBe('vitest browser smoke');
-  expect(globalThis.window).toBeDefined();
-});

tests/browser/toFormData.browser.test.js

@@ -0,0 +1,121 @@
+import { describe, expect, it } from 'vitest';
+
+import toFormData from '../../lib/helpers/toFormData.js';
+
+describe('helpers::toFormData (vitest browser)', () => {
+  it('converts nested data object to FormData with dots option enabled', () => {
+    const data = {
+      val: 123,
+      nested: {
+        arr: ['hello', 'world'],
+      },
+    };
+
+    const form = toFormData(data, null, { dots: true });
+
+    expect(form).toBeInstanceOf(FormData);
+    expect(Array.from(form.keys())).toHaveLength(3);
+    expect(form.get('val')).toBe('123');
+    expect(form.get('nested.arr.0')).toBe('hello');
+  });
+
+  it('respects metaTokens option', () => {
+    const data = {
+      'obj{}': { x: 1, y: 2 },
+    };
+    const serialized = JSON.stringify(data['obj{}']);
+
+    const form = toFormData(data, null, { metaTokens: false });
+
+    expect(Array.from(form.keys())).toHaveLength(1);
+    expect(form.getAll('obj')).toEqual([serialized]);
+  });
+
+  describe('flat arrays serialization', () => {
+    it('includes full indexes when indexes option is true', () => {
+      const data = {
+        arr: [1, 2, 3],
+        arr2: [1, [2], 3],
+      };
+
+      const form = toFormData(data, null, { indexes: true });
+
+      expect(Array.from(form.keys())).toHaveLength(6);
+      expect(form.get('arr[0]')).toBe('1');
+      expect(form.get('arr[1]')).toBe('2');
+      expect(form.get('arr[2]')).toBe('3');
+      expect(form.get('arr2[0]')).toBe('1');
+      expect(form.get('arr2[1][0]')).toBe('2');
+      expect(form.get('arr2[2]')).toBe('3');
+    });
+
+    it('includes brackets only when indexes option is false', () => {
+      const data = {
+        arr: [1, 2, 3],
+        arr2: [1, [2], 3],
+      };
+
+      const form = toFormData(data, null, { indexes: false });
+
+      expect(Array.from(form.keys())).toHaveLength(6);
+      expect(form.getAll('arr[]')).toEqual(['1', '2', '3']);
+      expect(form.get('arr2[0]')).toBe('1');
+      expect(form.get('arr2[1][0]')).toBe('2');
+      expect(form.get('arr2[2]')).toBe('3');
+    });
+
+    it('omits brackets when indexes option is null', () => {
+      const data = {
+        arr: [1, 2, 3],
+        arr2: [1, [2], 3],
+      };
+
+      const form = toFormData(data, null, { indexes: null });
+
+      expect(Array.from(form.keys())).toHaveLength(6);
+      expect(form.getAll('arr')).toEqual(['1', '2', '3']);
+      expect(form.get('arr2[0]')).toBe('1');
+      expect(form.get('arr2[1][0]')).toBe('2');
+      expect(form.get('arr2[2]')).toBe('3');
+    });
+  });
+
+  it('converts nested data object to FormData', () => {
+    const data = {
+      val: 123,
+      nested: {
+        arr: ['hello', 'world'],
+      },
+    };
+
+    const form = toFormData(data);
+
+    expect(form).toBeInstanceOf(FormData);
+    expect(Array.from(form.keys())).toHaveLength(3);
+    expect(form.get('val')).toBe('123');
+    expect(form.get('nested[arr][0]')).toBe('hello');
+  });
+
+  it('appends value whose key ends with [] as separate values with the same key', () => {
+    const data = {
+      'arr[]': [1, 2, 3],
+    };
+
+    const form = toFormData(data);
+
+    expect(Array.from(form.keys())).toHaveLength(3);
+    expect(form.getAll('arr[]')).toEqual(['1', '2', '3']);
+  });
+
+  it('appends value whose key ends with {} as a JSON string', () => {
+    const data = {
+      'obj{}': { x: 1, y: 2 },
+    };
+    const serialized = JSON.stringify(data['obj{}']);
+
+    const form = toFormData(data);
+
+    expect(Array.from(form.keys())).toHaveLength(1);
+    expect(form.getAll('obj{}')).toEqual([serialized]);
+  });
+});

tests/browser/transform.browser.test.js

@@ -0,0 +1,265 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import axios from '../../index.js';
+import AxiosError from '../../lib/core/AxiosError.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.responseHeaders = '';
+    this.readyState = 0;
+    this.status = 0;
+    this.statusText = '';
+    this.responseText = '';
+    this.response = null;
+    this.timeout = 0;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.onabort = null;
+    this.onerror = null;
+    this.ontimeout = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return this.responseHeaders;
+  }
+
+  send(data) {
+    this.params = data;
+    requests.push(this);
+  }
+
+  respondWith({ status = 200, statusText = 'OK', responseText = '', responseHeaders = '' } = {}) {
+    this.status = status;
+    this.statusText = statusText;
+    this.responseText = responseText;
+    this.response = responseText;
+    this.responseHeaders = responseHeaders;
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+
+  abort() {}
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const getLastRequest = () => {
+  const request = requests.at(-1);
+
+  expect(request).toBeDefined();
+
+  return request;
+};
+
+describe('transform (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+  });
+
+  it('should transform JSON to string', async () => {
+    const responsePromise = axios.post('/foo', { foo: 'bar' });
+    const request = getLastRequest();
+
+    expect(request.params).toBe('{"foo":"bar"}');
+
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should transform string to JSON', async () => {
+    const responsePromise = axios('/foo');
+    const request = getLastRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: '{"foo": "bar"}',
+    });
+
+    const response = await responsePromise;
+
+    expect(typeof response.data).toBe('object');
+    expect(response.data.foo).toBe('bar');
+  });
+
+  it('should throw a SyntaxError if JSON parsing failed and responseType is "json" if silentJSONParsing is false', async () => {
+    const responsePromise = axios({
+      url: '/foo',
+      responseType: 'json',
+      transitional: { silentJSONParsing: false },
+    });
+    const request = getLastRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: '{foo": "bar"}',
+    });
+
+    const thrown = await responsePromise.catch((error) => error);
+
+    expect(thrown).toBeTruthy();
+    expect(thrown.name).toContain('SyntaxError');
+    expect(thrown.code).toBe(AxiosError.ERR_BAD_RESPONSE);
+  });
+
+  it('should send data as JSON if request content-type is application/json', async () => {
+    const responsePromise = axios.post('/foo', 123, {
+      headers: { 'Content-Type': 'application/json' },
+    });
+    const request = getLastRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: '',
+    });
+
+    const response = await responsePromise;
+
+    expect(response).toBeTruthy();
+    expect(request.requestHeaders['Content-Type']).toBe('application/json');
+    expect(JSON.parse(request.params)).toBe(123);
+  });
+
+  it('should not assume JSON if responseType is not `json`', async () => {
+    const responsePromise = axios.get('/foo', {
+      responseType: 'text',
+      transitional: {
+        forcedJSONParsing: false,
+      },
+    });
+    const request = getLastRequest();
+    const rawData = '{"x":1}';
+
+    request.respondWith({
+      status: 200,
+      responseText: rawData,
+    });
+
+    const response = await responsePromise;
+
+    expect(response).toBeTruthy();
+    expect(response.data).toBe(rawData);
+  });
+
+  it('should override default transform', async () => {
+    const responsePromise = axios.post(
+      '/foo',
+      { foo: 'bar' },
+      {
+        transformRequest(data) {
+          return data;
+        },
+      }
+    );
+    const request = getLastRequest();
+
+    expect(typeof request.params).toBe('object');
+
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should allow an Array of transformers', async () => {
+    const responsePromise = axios.post(
+      '/foo',
+      { foo: 'bar' },
+      {
+        transformRequest: axios.defaults.transformRequest.concat(function (data) {
+          return data.replace('bar', 'baz');
+        }),
+      }
+    );
+    const request = getLastRequest();
+
+    expect(request.params).toBe('{"foo":"baz"}');
+
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should allowing mutating headers', async () => {
+    const token = Math.floor(Math.random() * Math.pow(2, 64)).toString(36);
+    const responsePromise = axios('/foo', {
+      transformRequest(data, headers) {
+        headers['X-Authorization'] = token;
+        return data;
+      },
+    });
+    const request = getLastRequest();
+
+    expect(request.requestHeaders['X-Authorization']).toBe(token);
+
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it("should normalize 'content-type' header when using a custom transformRequest", async () => {
+    const responsePromise = axios.post(
+      '/foo',
+      { foo: 'bar' },
+      {
+        headers: { 'content-type': 'application/x-www-form-urlencoded' },
+        transformRequest: [
+          function () {
+            return 'aa=44';
+          },
+        ],
+      }
+    );
+    const request = getLastRequest();
+
+    expect(request.requestHeaders['Content-Type']).toBe('application/x-www-form-urlencoded');
+
+    request.respondWith();
+    await responsePromise;
+  });
+
+  it('should return response.data as parsed JSON object when responseType is json', async () => {
+    const instance = axios.create({
+      baseURL: '/api',
+      responseType: 'json',
+    });
+    const responsePromise = instance.get('my/endpoint', { responseType: 'json' });
+    const request = getLastRequest();
+
+    request.respondWith({
+      status: 200,
+      responseText: '{"key1": "value1"}',
+      responseHeaders: 'content-type: application/json',
+    });
+
+    const response = await responsePromise;
+
+    expect(response).toBeTruthy();
+    expect(response.data).toEqual({ key1: 'value1' });
+  });
+});

tests/browser/xsrf.browser.test.js

@@ -0,0 +1,182 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import axios from '../../index.js';
+import cookies from '../../lib/helpers/cookies.js';
+
+class MockXMLHttpRequest {
+  constructor() {
+    this.requestHeaders = {};
+    this.readyState = 0;
+    this.status = 200;
+    this.statusText = 'OK';
+    this.responseText = '';
+    this.timeout = 0;
+    this.onreadystatechange = null;
+    this.onloadend = null;
+    this.onabort = null;
+    this.onerror = null;
+    this.ontimeout = null;
+    this.upload = {
+      addEventListener() {},
+    };
+  }
+
+  open(method, url, async = true) {
+    this.method = method;
+    this.url = url;
+    this.async = async;
+  }
+
+  setRequestHeader(key, value) {
+    this.requestHeaders[key] = value;
+  }
+
+  addEventListener() {}
+
+  getAllResponseHeaders() {
+    return '';
+  }
+
+  send() {
+    requests.push(this);
+    this.readyState = 4;
+
+    queueMicrotask(() => {
+      if (this.onloadend) {
+        this.onloadend();
+      } else if (this.onreadystatechange) {
+        this.onreadystatechange();
+      }
+    });
+  }
+
+  abort() {}
+}
+
+let requests = [];
+let OriginalXMLHttpRequest;
+
+const setXsrfCookie = (value) => {
+  document.cookie = `${axios.defaults.xsrfCookieName}=${value}; path=/`;
+};
+
+const clearXsrfCookie = () => {
+  document.cookie = `${axios.defaults.xsrfCookieName}=; expires=${new Date(
+    Date.now() - 86400000
+  ).toUTCString()}; path=/`;
+};
+
+const sendRequest = async (url, config) => {
+  const responsePromise = axios(url, config);
+  const request = requests.at(-1);
+
+  expect(request).toBeDefined();
+  await responsePromise;
+
+  return request;
+};
+
+describe('xsrf (vitest browser)', () => {
+  beforeEach(() => {
+    requests = [];
+    OriginalXMLHttpRequest = window.XMLHttpRequest;
+    window.XMLHttpRequest = MockXMLHttpRequest;
+  });
+
+  afterEach(() => {
+    clearXsrfCookie();
+    window.XMLHttpRequest = OriginalXMLHttpRequest;
+    vi.restoreAllMocks();
+  });
+
+  it('should not set xsrf header if cookie is null', async () => {
+    const request = await sendRequest('/foo');
+
+    expect(request.requestHeaders[axios.defaults.xsrfHeaderName]).toBeUndefined();
+  });
+
+  it('should set xsrf header if cookie is set', async () => {
+    setXsrfCookie('12345');
+
+    const request = await sendRequest('/foo');
+
+    expect(request.requestHeaders[axios.defaults.xsrfHeaderName]).toBe('12345');
+  });
+
+  it('should not set xsrf header if xsrfCookieName is null', async () => {
+    setXsrfCookie('12345');
+
+    const request = await sendRequest('/foo', {
+      xsrfCookieName: null,
+    });
+
+    expect(request.requestHeaders[axios.defaults.xsrfHeaderName]).toBeUndefined();
+  });
+
+  it('should not read cookies at all if xsrfCookieName is null', async () => {
+    const readSpy = vi.spyOn(cookies, 'read');
+
+    await sendRequest('/foo', {
+      xsrfCookieName: null,
+    });
+
+    expect(readSpy).not.toHaveBeenCalled();
+  });
+
+  it('should not set xsrf header for cross origin', async () => {
+    setXsrfCookie('12345');
+
+    const request = await sendRequest('http://example.com/');
+
+    expect(request.requestHeaders[axios.defaults.xsrfHeaderName]).toBeUndefined();
+  });
+
+  it('should not set xsrf header for cross origin when using withCredentials', async () => {
+    setXsrfCookie('12345');
+
+    const request = await sendRequest('http://example.com/', {
+      withCredentials: true,
+    });
+
+    expect(request.requestHeaders[axios.defaults.xsrfHeaderName]).toBeUndefined();
+  });
+
+  describe('withXSRFToken option', () => {
+    it('should set xsrf header for cross origin when withXSRFToken = true', async () => {
+      const token = '12345';
+
+      setXsrfCookie(token);
+
+      const request = await sendRequest('http://example.com/', {
+        withXSRFToken: true,
+      });
+
+      expect(request.requestHeaders[axios.defaults.xsrfHeaderName]).toBe(token);
+    });
+
+    it('should not set xsrf header for the same origin when withXSRFToken = false', async () => {
+      const token = '12345';
+
+      setXsrfCookie(token);
+
+      const request = await sendRequest('/foo', {
+        withXSRFToken: false,
+      });
+
+      expect(request.requestHeaders[axios.defaults.xsrfHeaderName]).toBeUndefined();
+    });
+
+    it('should support function resolver', async () => {
+      const token = '12345';
+
+      setXsrfCookie(token);
+
+      const request = await sendRequest('/foo', {
+        withXSRFToken: (config) => config.userFlag === 'yes',
+        userFlag: 'yes',
+      });
+
+      expect(request.requestHeaders[axios.defaults.xsrfHeaderName]).toBe(token);
+    });
+  });
+});

tests/setup/server.js

@@ -6,8 +6,6 @@ import { Throttle } from 'stream-throttle';
 import formidable from 'formidable';
 import selfsigned from 'selfsigned';
 
-export const LOCAL_SERVER_URL = 'http://localhost:4444';
-
 export const SERVER_HANDLER_STREAM_ECHO = (req, res) => req.pipe(res);
 
 export const setTimeoutAsync = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

tests/smoke/cjs/package.json

@@ -0,0 +1,19 @@
+{
+  "name": "@axios/cjs-smoke-tests",
+  "version": "1.0.0",
+  "description": "CJS smoke tests for axios",
+  "private": true,
+  "scripts": {
+    "test:smoke:cjs:mocha": "mocha \"tests/**/*.smoke.test.cjs\""
+  },
+  "keywords": [],
+  "author": "axios team",
+  "license": "MIT",
+  "dependencies": {
+    "axios": "file:../../../"
+  },
+  "devDependencies": {
+    "mocha": "9.2.2",
+    "chai": "4.5.0"
+  }
+}

tests/smoke/cjs/tests/auth.smoke.test.cjs

@@ -0,0 +1,137 @@
+const http = require('http');
+const axios = require('axios');
+const { describe, it, afterEach } = require('mocha');
+const { expect } = require('chai');
+
+const startServer = (handler) => {
+  return new Promise((resolve) => {
+    const server = http.createServer(handler);
+
+    server.listen(0, '127.0.0.1', () => {
+      resolve(server);
+    });
+  });
+};
+
+const stopServer = (server) => {
+  if (!server || !server.listening) {
+    return Promise.resolve();
+  }
+
+  return new Promise((resolve, reject) => {
+    server.close((error) => {
+      if (error) {
+        reject(error);
+        return;
+      }
+      resolve();
+    });
+  });
+};
+
+describe('auth compat (dist export only)', () => {
+  let server;
+
+  afterEach(async () => {
+    await stopServer(server);
+    server = undefined;
+  });
+
+  const requestWithConfig = async (config) => {
+    server = await startServer((req, res) => {
+      res.setHeader('Content-Type', 'text/plain');
+      res.end(req.headers.authorization || '');
+    });
+
+    const { port } = server.address();
+
+    return axios.get(
+      `http://127.0.0.1:${port}/`,
+      Object.assign(
+        {
+          proxy: false,
+        },
+        config || {}
+      )
+    );
+  };
+
+  it('sets Basic Authorization header from auth credentials', async () => {
+    const response = await requestWithConfig({
+      auth: {
+        username: 'janedoe',
+        password: 's00pers3cret',
+      },
+    });
+
+    const expected = `Basic ${Buffer.from('janedoe:s00pers3cret', 'utf8').toString('base64')}`;
+
+    expect(response.data).to.equal(expected);
+  });
+
+  it('supports auth without password', async () => {
+    const response = await requestWithConfig({
+      auth: {
+        username: 'Aladdin',
+      },
+    });
+
+    const expected = `Basic ${Buffer.from('Aladdin:', 'utf8').toString('base64')}`;
+
+    expect(response.data).to.equal(expected);
+  });
+
+  it('overwrites an existing Authorization header when auth is provided', async () => {
+    const response = await requestWithConfig({
+      headers: {
+        Authorization: 'Bearer token-123',
+      },
+      auth: {
+        username: 'foo',
+        password: 'bar',
+      },
+    });
+
+    const expected = `Basic ${Buffer.from('foo:bar', 'utf8').toString('base64')}`;
+
+    expect(response.data).to.equal(expected);
+  });
+
+  it('uses URL credentials when auth config is not provided (node adapter behavior)', async () => {
+    server = await startServer((req, res) => {
+      res.setHeader('Content-Type', 'text/plain');
+      res.end(req.headers.authorization || '');
+    });
+
+    const { port } = server.address();
+
+    const response = await axios.get(`http://urluser:urlpass@127.0.0.1:${port}/`, {
+      proxy: false,
+    });
+
+    const expected = `Basic ${Buffer.from('urluser:urlpass', 'utf8').toString('base64')}`;
+
+    expect(response.data).to.equal(expected);
+  });
+
+  it('prefers auth config over URL credentials', async () => {
+    server = await startServer((req, res) => {
+      res.setHeader('Content-Type', 'text/plain');
+      res.end(req.headers.authorization || '');
+    });
+
+    const { port } = server.address();
+
+    const response = await axios.get(`http://urluser:urlpass@127.0.0.1:${port}/`, {
+      proxy: false,
+      auth: {
+        username: 'configuser',
+        password: 'configpass',
+      },
+    });
+
+    const expected = `Basic ${Buffer.from('configuser:configpass', 'utf8').toString('base64')}`;
+
+    expect(response.data).to.equal(expected);
+  });
+});

tests/smoke/cjs/tests/basic.smoke.test.cjs

@@ -0,0 +1,145 @@
+const { EventEmitter } = require('events');
+const { PassThrough } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const createTransportCapture = () => {
+  let capturedOptions;
+
+  const transport = {
+    request(options, onResponse) {
+      capturedOptions = options;
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.end = () => {
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end('{"ok":true}');
+      };
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCapturedOptions: () => capturedOptions,
+  };
+};
+
+const runRequest = async (run) => {
+  const { transport, getCapturedOptions } = createTransportCapture();
+  await run(transport);
+
+  return getCapturedOptions();
+};
+
+describe('basic compat (dist export only)', () => {
+  it('supports the simplest axios(url) request pattern', async () => {
+    const options = await runRequest((transport) =>
+      axios('http://example.com/users', {
+        transport,
+        proxy: false,
+      })
+    );
+
+    expect(options.method).to.equal('GET');
+    expect(options.path).to.equal('/users');
+  });
+
+  it('supports get()', async () => {
+    const options = await runRequest((transport) =>
+      axios.get('http://example.com/items?limit=10', { transport, proxy: false })
+    );
+
+    expect(options.method).to.equal('GET');
+    expect(options.path).to.equal('/items?limit=10');
+  });
+
+  it('supports delete()', async () => {
+    const options = await runRequest((transport) =>
+      axios.delete('http://example.com/items/1', { transport, proxy: false })
+    );
+
+    expect(options.method).to.equal('DELETE');
+    expect(options.path).to.equal('/items/1');
+  });
+
+  it('supports head()', async () => {
+    const options = await runRequest((transport) =>
+      axios.head('http://example.com/health', { transport, proxy: false })
+    );
+
+    expect(options.method).to.equal('HEAD');
+    expect(options.path).to.equal('/health');
+  });
+
+  it('supports options()', async () => {
+    const options = await runRequest((transport) =>
+      axios.options('http://example.com/items', { transport, proxy: false })
+    );
+
+    expect(options.method).to.equal('OPTIONS');
+    expect(options.path).to.equal('/items');
+  });
+
+  it('supports post()', async () => {
+    const options = await runRequest((transport) =>
+      axios.post(
+        'http://example.com/items',
+        { name: 'widget' },
+        {
+          transport,
+          proxy: false,
+        }
+      )
+    );
+
+    expect(options.method).to.equal('POST');
+    expect(options.path).to.equal('/items');
+  });
+
+  it('supports put()', async () => {
+    const options = await runRequest((transport) =>
+      axios.put(
+        'http://example.com/items/1',
+        { name: 'updated-widget' },
+        {
+          transport,
+          proxy: false,
+        }
+      )
+    );
+
+    expect(options.method).to.equal('PUT');
+    expect(options.path).to.equal('/items/1');
+  });
+
+  it('supports patch()', async () => {
+    const options = await runRequest((transport) =>
+      axios.patch(
+        'http://example.com/items/1',
+        { status: 'active' },
+        {
+          transport,
+          proxy: false,
+        }
+      )
+    );
+
+    expect(options.method).to.equal('PATCH');
+    expect(options.path).to.equal('/items/1');
+  });
+});

tests/smoke/cjs/tests/cancel.smoke.test.cjs

@@ -0,0 +1,117 @@
+const { EventEmitter } = require('events');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const NODE_VERSION = parseInt(process.versions.node.split('.')[0]);
+const itWithAbortController = NODE_VERSION < 16 ? it.skip : it;
+
+const createPendingTransport = () => {
+  let requestCount = 0;
+
+  const transport = {
+    request() {
+      requestCount += 1;
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.end = () => {};
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getRequestCount: () => requestCount,
+  };
+};
+
+describe('cancel compat (dist export only)', () => {
+  itWithAbortController(
+    'supports cancellation with AbortController (pre-aborted signal)',
+    async () => {
+      const { transport, getRequestCount } = createPendingTransport();
+      const controller = new AbortController();
+      controller.abort();
+
+      try {
+        const request = axios.get('http://example.com/resource', {
+          signal: controller.signal,
+          transport,
+          proxy: false,
+        });
+
+        controller.abort();
+        await request;
+      } catch (error) {
+        expect(error).to.have.property('code', 'ERR_CANCELED');
+      }
+
+      expect(getRequestCount()).to.equal(0);
+    }
+  );
+
+  itWithAbortController('supports cancellation with AbortController (in-flight)', async () => {
+    const { transport, getRequestCount } = createPendingTransport();
+    const controller = new AbortController();
+
+    try {
+      const request = axios.get('http://example.com/resource', {
+        signal: controller.signal,
+        transport,
+        proxy: false,
+      });
+
+      controller.abort();
+      await request;
+    } catch (error) {
+      expect(error).to.have.property('code', 'ERR_CANCELED');
+    }
+
+    expect(getRequestCount()).to.equal(1);
+  });
+
+  it('supports cancellation with CancelToken (pre-canceled token)', async () => {
+    const { transport, getRequestCount } = createPendingTransport();
+    const source = axios.CancelToken.source();
+    source.cancel('Operation canceled by the user.');
+
+    const error = await axios
+      .get('http://example.com/resource', {
+        cancelToken: source.token,
+        transport,
+        proxy: false,
+      })
+      .catch((err) => err);
+
+    expect(axios.isCancel(error)).to.be.true;
+    expect(error.code).to.equal('ERR_CANCELED');
+    expect(getRequestCount()).to.equal(0);
+  });
+
+  it('supports cancellation with CancelToken (in-flight)', async () => {
+    const { transport, getRequestCount } = createPendingTransport();
+    const source = axios.CancelToken.source();
+
+    const request = axios.get('http://example.com/resource', {
+      cancelToken: source.token,
+      transport,
+      proxy: false,
+    });
+
+    source.cancel('Operation canceled by the user.');
+
+    const error = await request.catch((err) => err);
+
+    expect(axios.isCancel(error)).to.be.true;
+    expect(error.code).to.equal('ERR_CANCELED');
+    expect(getRequestCount()).to.equal(1);
+  });
+});

tests/smoke/cjs/tests/error.smoke.test.cjs

@@ -0,0 +1,137 @@
+const { EventEmitter } = require('events');
+const { PassThrough } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const createTransport = (config) => {
+  const opts = config || {};
+
+  return {
+    request(options, onResponse) {
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.write = () => true;
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+
+      req.setTimeout = (_ms, cb) => {
+        if (opts.timeout) {
+          req._timeoutCallback = cb;
+        }
+      };
+
+      req.end = () => {
+        if (opts.error) {
+          req.emit('error', opts.error);
+          return;
+        }
+
+        if (opts.timeout && req._timeoutCallback) {
+          req._timeoutCallback();
+          return;
+        }
+
+        const res = new PassThrough();
+        res.statusCode =
+          opts.response && opts.response.statusCode !== undefined ? opts.response.statusCode : 200;
+        res.statusMessage =
+          opts.response && opts.response.statusMessage ? opts.response.statusMessage : 'OK';
+        res.headers =
+          opts.response && opts.response.headers
+            ? opts.response.headers
+            : { 'content-type': 'application/json' };
+        res.req = req;
+
+        onResponse(res);
+        res.end(opts.response && opts.response.body ? opts.response.body : '{"ok":true}');
+      };
+
+      return req;
+    },
+  };
+};
+
+describe('error compat (dist export only)', () => {
+  it('rejects with AxiosError for non-2xx responses by default', async () => {
+    const err = await axios
+      .get('http://example.com/fail', {
+        proxy: false,
+        transport: createTransport({
+          response: {
+            statusCode: 500,
+            statusMessage: 'Internal Server Error',
+            body: '{"error":"boom"}',
+          },
+        }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).to.be.true;
+    expect(err.response.status).to.equal(500);
+    expect(err.message).to.include('500');
+  });
+
+  it('resolves when validateStatus allows non-2xx responses', async () => {
+    const response = await axios.get('http://example.com/allowed', {
+      proxy: false,
+      validateStatus: () => true,
+      transport: createTransport({
+        response: {
+          statusCode: 500,
+          statusMessage: 'Internal Server Error',
+          body: '{"ok":false}',
+        },
+      }),
+    });
+
+    expect(response.status).to.equal(500);
+    expect(response.data).to.deep.equal({ ok: false });
+  });
+
+  it('wraps transport errors as AxiosError', async () => {
+    const err = await axios
+      .get('http://example.com/network', {
+        proxy: false,
+        transport: createTransport({
+          error: new Error('socket hang up'),
+        }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).to.be.true;
+    expect(err.message).to.include('socket hang up');
+    expect(err.toJSON).to.be.a('function');
+  });
+
+  it('rejects with ECONNABORTED on timeout', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: 10,
+        transport: createTransport({ timeout: true }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).to.be.true;
+    expect(err.code).to.equal('ECONNABORTED');
+    expect(err.message).to.equal('timeout of 10ms exceeded');
+  });
+
+  it('uses timeoutErrorMessage when provided', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: 25,
+        timeoutErrorMessage: 'custom timeout message',
+        transport: createTransport({ timeout: true }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).to.be.true;
+    expect(err.code).to.equal('ECONNABORTED');
+    expect(err.message).to.equal('custom timeout message');
+  });
+});

tests/smoke/cjs/tests/fetch.smoke.test.cjs

@@ -0,0 +1,145 @@
+const axios = require('axios');
+const { it, describe } = require('mocha');
+const { expect } = require('chai');
+
+const NODE_VERSION = parseInt(process.versions.node.split('.')[0]);
+const describeWithFetch = NODE_VERSION < 18 ? describe.skip : describe;
+
+const createFetchMock = (responseFactory) => {
+  const calls = [];
+
+  const mockFetch = async (input, init) => {
+    calls.push({ input, init: init || {} });
+
+    if (responseFactory) {
+      return responseFactory(input, init || {});
+    }
+
+    return new Response(JSON.stringify({ ok: true }), {
+      status: 200,
+      headers: { 'Content-Type': 'application/json' },
+    });
+  };
+
+  return {
+    mockFetch,
+    getCalls: () => calls,
+  };
+};
+
+describeWithFetch('fetch compat (dist export only)', () => {
+  it('uses fetch adapter and resolves JSON response', async () => {
+    const { mockFetch, getCalls } = createFetchMock();
+
+    const response = await axios.get('https://example.com/users', {
+      adapter: 'fetch',
+      env: {
+        fetch: mockFetch,
+        Request,
+        Response,
+      },
+    });
+
+    expect(response.data).to.deep.equal({ ok: true });
+    expect(response.status).to.equal(200);
+    expect(getCalls()).to.have.lengthOf(1);
+  });
+
+  it('sends method, headers and body for post requests', async () => {
+    const { mockFetch, getCalls } = createFetchMock(async (input, init) => {
+      const requestInit = init || {};
+      const isRequest = input && typeof input !== 'string';
+      const method = isRequest ? input.method : requestInit.method;
+
+      const body =
+        isRequest && typeof input.clone === 'function'
+          ? await input.clone().text()
+          : requestInit.body;
+
+      let contentType;
+      if (isRequest && input.headers) {
+        contentType = input.headers.get('content-type');
+      } else if (requestInit.headers) {
+        contentType = requestInit.headers['Content-Type'] || requestInit.headers['content-type'];
+      }
+
+      return new Response(
+        JSON.stringify({
+          url: typeof input === 'string' ? input : input.url,
+          method,
+          contentType,
+          body,
+        }),
+        {
+          status: 200,
+          headers: { 'Content-Type': 'application/json' },
+        }
+      );
+    });
+
+    const response = await axios.post(
+      'https://example.com/items',
+      { name: 'widget' },
+      {
+        adapter: 'fetch',
+        env: {
+          fetch: mockFetch,
+          Request,
+          Response,
+        },
+      }
+    );
+
+    expect(getCalls()).to.have.lengthOf(1);
+    expect(response.data.url).to.equal('https://example.com/items');
+    expect(response.data.method).to.equal('POST');
+    expect(response.data.contentType).to.include('application/json');
+    expect(response.data.body).to.equal(JSON.stringify({ name: 'widget' }));
+  });
+
+  it('rejects non-2xx fetch responses by default', async () => {
+    const { mockFetch } = createFetchMock(
+      () =>
+        new Response(JSON.stringify({ error: 'boom' }), {
+          status: 500,
+          statusText: 'Internal Server Error',
+          headers: { 'Content-Type': 'application/json' },
+        })
+    );
+
+    const err = await axios
+      .get('https://example.com/fail', {
+        adapter: 'fetch',
+        env: {
+          fetch: mockFetch,
+          Request,
+          Response,
+        },
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).to.be.true;
+    expect(err.response.status).to.equal(500);
+  });
+
+  it('supports cancellation with AbortController in fetch mode', async () => {
+    const { mockFetch } = createFetchMock();
+    const controller = new AbortController();
+    controller.abort();
+
+    const err = await axios
+      .get('https://example.com/cancel', {
+        adapter: 'fetch',
+        signal: controller.signal,
+        env: {
+          fetch: mockFetch,
+          Request,
+          Response,
+        },
+      })
+      .catch((e) => e);
+
+    expect(axios.isCancel(err)).to.be.true;
+    expect(err.code).to.equal('ERR_CANCELED');
+  });
+});

tests/smoke/cjs/tests/files.smoke.test.cjs

@@ -0,0 +1,115 @@
+const { PassThrough, Readable, Writable } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const createCaptureTransport = (buildResponse) => {
+  return {
+    request(options, onResponse) {
+      const chunks = [];
+
+      const req = new Writable({
+        write(chunk, _encoding, callback) {
+          chunks.push(Buffer.from(chunk));
+          callback();
+        },
+      });
+
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.close = () => {
+        req.destroyed = true;
+      };
+
+      const originalDestroy = req.destroy.bind(req);
+      req.destroy = (...args) => {
+        req.destroyed = true;
+        return originalDestroy(...args);
+      };
+
+      const originalEnd = req.end.bind(req);
+      req.end = (...args) => {
+        originalEnd(...args);
+
+        const body = Buffer.concat(chunks);
+        const response = buildResponse ? buildResponse(body, options) : {};
+
+        const res = new PassThrough();
+        res.statusCode = response.statusCode !== undefined ? response.statusCode : 200;
+        res.statusMessage = response.statusMessage || 'OK';
+        res.headers = response.headers || { 'content-type': 'application/json' };
+        res.req = req;
+
+        onResponse(res);
+        res.end(response.body || JSON.stringify({ size: body.length }));
+      };
+
+      req.on('error', () => {});
+      return req;
+    },
+  };
+};
+
+describe('files compat (dist export only)', () => {
+  it('supports posting Buffer payloads', async () => {
+    const source = Buffer.from('binary-\x00-data', 'utf8');
+
+    const response = await axios.post('http://example.com/upload', source, {
+      proxy: false,
+      transport: createCaptureTransport((body) => ({
+        body: JSON.stringify({ echoed: body.toString('base64') }),
+      })),
+    });
+
+    expect(response.data.echoed).to.equal(source.toString('base64'));
+  });
+
+  it('supports posting Uint8Array payloads', async () => {
+    const source = Uint8Array.from([1, 2, 3, 4, 255]);
+
+    const response = await axios.post('http://example.com/upload', source, {
+      proxy: false,
+      transport: createCaptureTransport((body) => ({
+        body: JSON.stringify({ echoed: Array.from(body.values()) }),
+      })),
+    });
+
+    expect(response.data.echoed).to.deep.equal([1, 2, 3, 4, 255]);
+  });
+
+  it('supports posting Readable stream payloads', async () => {
+    const streamData = ['hello ', 'stream ', 'world'];
+    const source = Readable.from(streamData);
+
+    const response = await axios.post('http://example.com/upload', source, {
+      proxy: false,
+      headers: { 'Content-Type': 'application/octet-stream' },
+      transport: createCaptureTransport((body, options) => ({
+        body: JSON.stringify({
+          text: body.toString('utf8'),
+          contentType:
+            options.headers && (options.headers['Content-Type'] || options.headers['content-type']),
+        }),
+      })),
+    });
+
+    expect(response.data.text).to.equal('hello stream world');
+    expect(response.data.contentType).to.contain('application/octet-stream');
+  });
+
+  it('supports binary downloads with responseType=arraybuffer', async () => {
+    const binary = Buffer.from([0xde, 0xad, 0xbe, 0xef]);
+
+    const response = await axios.get('http://example.com/file.bin', {
+      proxy: false,
+      responseType: 'arraybuffer',
+      transport: createCaptureTransport(() => ({
+        headers: { 'content-type': 'application/octet-stream' },
+        body: binary,
+      })),
+    });
+
+    expect(Buffer.isBuffer(response.data)).to.equal(true);
+    expect(response.data.equals(binary)).to.equal(true);
+  });
+});

tests/smoke/cjs/tests/formData.smoke.test.cjs

@@ -0,0 +1,110 @@
+const { Writable, PassThrough } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const NODE_VERSION = parseInt(process.versions.node.split('.')[0]);
+const describeWithFormData = NODE_VERSION < 18 ? describe.skip : describe;
+
+const createCaptureTransport = (buildResponse) => {
+  return {
+    request(options, onResponse) {
+      const chunks = [];
+
+      const req = new Writable({
+        write(chunk, _encoding, callback) {
+          chunks.push(Buffer.from(chunk));
+          callback();
+        },
+      });
+
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = req.write.bind(req);
+      req.close = () => {
+        req.destroyed = true;
+      };
+
+      const originalDestroy = req.destroy.bind(req);
+      req.destroy = (...args) => {
+        req.destroyed = true;
+        return originalDestroy(...args);
+      };
+
+      const originalEnd = req.end.bind(req);
+      req.end = (...args) => {
+        originalEnd(...args);
+
+        const body = Buffer.concat(chunks);
+        const response = buildResponse ? buildResponse(body, options) : {};
+
+        const res = new PassThrough();
+        res.statusCode = response.statusCode !== undefined ? response.statusCode : 200;
+        res.statusMessage = response.statusMessage || 'OK';
+        res.headers = response.headers || { 'content-type': 'application/json' };
+        res.req = req;
+
+        onResponse(res);
+        res.end(response.body || JSON.stringify({ ok: true }));
+      };
+
+      return req;
+    },
+  };
+};
+
+const bodyAsUtf8 = (value) => {
+  return Buffer.isBuffer(value) ? value.toString('utf8') : String(value);
+};
+
+describeWithFormData('formData compat (dist export only)', () => {
+  it('supports posting FormData instances', async () => {
+    const form = new FormData();
+    form.append('username', 'janedoe');
+    form.append('role', 'admin');
+
+    const response = await axios.post('http://example.com/form', form, {
+      proxy: false,
+      transport: createCaptureTransport((body, options) => ({
+        body: JSON.stringify({
+          contentType:
+            options.headers && (options.headers['Content-Type'] || options.headers['content-type']),
+          payload: bodyAsUtf8(body),
+        }),
+      })),
+    });
+
+    expect(response.data.contentType).to.contain('multipart/form-data');
+    expect(response.data.payload).to.contain('name="username"');
+    expect(response.data.payload).to.contain('janedoe');
+    expect(response.data.payload).to.contain('name="role"');
+    expect(response.data.payload).to.contain('admin');
+  });
+
+  it('supports axios.postForm helper', async () => {
+    const response = await axios.postForm(
+      'http://example.com/post-form',
+      {
+        project: 'axios',
+        mode: 'compat',
+      },
+      {
+        proxy: false,
+        transport: createCaptureTransport((body, options) => ({
+          body: JSON.stringify({
+            contentType:
+              options.headers &&
+              (options.headers['Content-Type'] || options.headers['content-type']),
+            payload: bodyAsUtf8(body),
+          }),
+        })),
+      }
+    );
+
+    expect(response.data.contentType).to.contain('multipart/form-data');
+    expect(response.data.payload).to.contain('name="project"');
+    expect(response.data.payload).to.contain('axios');
+    expect(response.data.payload).to.contain('name="mode"');
+    expect(response.data.payload).to.contain('compat');
+  });
+});

tests/smoke/cjs/tests/headers.smoke.test.cjs

@@ -0,0 +1,125 @@
+const { EventEmitter } = require('events');
+const { PassThrough } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const normalizeHeaders = (headers) => {
+  const result = {};
+
+  Object.entries(headers || {}).forEach(([key, value]) => {
+    result[key.toLowerCase()] = value;
+  });
+
+  return result;
+};
+
+const createTransportCapture = () => {
+  let capturedOptions;
+
+  const transport = {
+    request(options, onResponse) {
+      capturedOptions = options;
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+      req.end = () => {
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end('{"ok":true}');
+      };
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCapturedOptions: () => capturedOptions,
+  };
+};
+
+describe('headers compat (dist export only)', () => {
+  it('sends default Accept header', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    await axios.get('http://example.com/default-headers', {
+      transport,
+      proxy: false,
+    });
+
+    const headers = normalizeHeaders(getCapturedOptions().headers);
+    expect(headers.accept).to.equal('application/json, text/plain, */*');
+  });
+
+  it('supports custom headers', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    await axios.get('http://example.com/custom-headers', {
+      transport,
+      proxy: false,
+      headers: {
+        'X-Trace-Id': 'trace-123',
+        Authorization: 'Bearer token-abc',
+      },
+    });
+
+    const headers = normalizeHeaders(getCapturedOptions().headers);
+    expect(headers['x-trace-id']).to.equal('trace-123');
+    expect(headers.authorization).to.equal('Bearer token-abc');
+  });
+
+  it('treats header names as case-insensitive when overriding', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    await axios.get('http://example.com/case-insensitive', {
+      transport,
+      proxy: false,
+      headers: {
+        authorization: 'Bearer old-token',
+        AuThOrIzAtIoN: 'Bearer new-token',
+      },
+    });
+
+    const headers = normalizeHeaders(getCapturedOptions().headers);
+    expect(headers.authorization).to.equal('Bearer new-token');
+  });
+
+  it('sets content-type for json post payloads', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    await axios.post(
+      'http://example.com/post-json',
+      { name: 'widget' },
+      {
+        transport,
+        proxy: false,
+      }
+    );
+
+    const headers = normalizeHeaders(getCapturedOptions().headers);
+    expect(headers['content-type']).to.contain('application/json');
+  });
+
+  it('does not force content-type for get requests without body', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    await axios.get('http://example.com/get-no-body', {
+      transport,
+      proxy: false,
+    });
+
+    const headers = normalizeHeaders(getCapturedOptions().headers);
+    expect(headers['content-type']).to.be.undefined;
+  });
+});

tests/smoke/cjs/tests/http2.smoke.test.cjs

@@ -0,0 +1,86 @@
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+describe('http2 compat (dist export only)', () => {
+  it('keeps instance-level httpVersion and http2Options in request config', async () => {
+    const client = axios.create({
+      baseURL: 'https://example.com',
+      httpVersion: 2,
+      http2Options: {
+        rejectUnauthorized: false,
+      },
+    });
+
+    const response = await client.get('/resource', {
+      adapter: async (config) => ({
+        data: {
+          httpVersion: config.httpVersion,
+          http2Options: config.http2Options,
+        },
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data.httpVersion).to.equal(2);
+    expect(response.data.http2Options).to.deep.equal({
+      rejectUnauthorized: false,
+    });
+  });
+
+  it('merges request http2Options with instance http2Options', async () => {
+    const client = axios.create({
+      baseURL: 'https://example.com',
+      httpVersion: 2,
+      http2Options: {
+        rejectUnauthorized: false,
+        sessionTimeout: 1000,
+      },
+    });
+
+    const response = await client.get('/resource', {
+      http2Options: {
+        sessionTimeout: 5000,
+        customFlag: true,
+      },
+      adapter: async (config) => ({
+        data: config.http2Options,
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data).to.deep.equal({
+      rejectUnauthorized: false,
+      sessionTimeout: 5000,
+      customFlag: true,
+    });
+  });
+
+  it('allows request-level httpVersion override', async () => {
+    const client = axios.create({
+      baseURL: 'https://example.com',
+      httpVersion: 2,
+    });
+
+    const response = await client.get('/resource', {
+      httpVersion: 1,
+      adapter: async (config) => ({
+        data: {
+          httpVersion: config.httpVersion,
+        },
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data.httpVersion).to.equal(1);
+  });
+});

tests/smoke/cjs/tests/instance.smoke.test.cjs

@@ -0,0 +1,146 @@
+const { EventEmitter } = require('events');
+const { PassThrough } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const createTransportCapture = (responseBody) => {
+  const calls = [];
+
+  const transport = {
+    request(options, onResponse) {
+      calls.push(options);
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+      req.end = () => {
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end(responseBody || '{"ok":true}');
+      };
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCalls: () => calls,
+  };
+};
+
+describe('instance compat (dist export only)', () => {
+  it('creates isolated instances with separate defaults', async () => {
+    const { transport, getCalls } = createTransportCapture();
+
+    const clientA = axios.create({
+      baseURL: 'http://example.com/api-a',
+      headers: {
+        'X-App': 'A',
+      },
+    });
+    const clientB = axios.create({
+      baseURL: 'http://example.com/api-b',
+      headers: {
+        'X-App': 'B',
+      },
+    });
+
+    await clientA.get('/users', { transport, proxy: false });
+    await clientB.get('/users', { transport, proxy: false });
+
+    const [callA, callB] = getCalls();
+    expect(callA.path).to.equal('/api-a/users');
+    expect(callB.path).to.equal('/api-b/users');
+    expect(callA.headers['X-App']).to.equal('A');
+    expect(callB.headers['X-App']).to.equal('B');
+  });
+
+  it('supports callable instance form instance(config)', async () => {
+    const { transport, getCalls } = createTransportCapture();
+    const client = axios.create({
+      baseURL: 'http://example.com',
+    });
+
+    await client({
+      url: '/status',
+      method: 'get',
+      transport,
+      proxy: false,
+    });
+
+    expect(getCalls()).to.have.lengthOf(1);
+    expect(getCalls()[0].method).to.equal('GET');
+    expect(getCalls()[0].path).to.equal('/status');
+  });
+
+  it('applies instance request interceptors', async () => {
+    const { transport, getCalls } = createTransportCapture();
+    const client = axios.create({
+      baseURL: 'http://example.com',
+    });
+
+    client.interceptors.request.use((config) => {
+      config.headers = config.headers || {};
+      config.headers['X-From-Interceptor'] = 'yes';
+      return config;
+    });
+
+    await client.get('/intercepted', { transport, proxy: false });
+
+    expect(getCalls()).to.have.lengthOf(1);
+    expect(getCalls()[0].headers['X-From-Interceptor']).to.equal('yes');
+  });
+
+  it('applies instance response interceptors', async () => {
+    const { transport } = createTransportCapture('{"name":"axios"}');
+    const client = axios.create({
+      baseURL: 'http://example.com',
+    });
+
+    client.interceptors.response.use((response) => {
+      response.data = Object.assign({}, response.data, {
+        intercepted: true,
+      });
+      return response;
+    });
+
+    const response = await client.get('/response-interceptor', {
+      transport,
+      proxy: false,
+    });
+
+    expect(response.data).to.deep.equal({
+      name: 'axios',
+      intercepted: true,
+    });
+  });
+
+  it('builds URLs with getUri from instance defaults and request params', () => {
+    const client = axios.create({
+      baseURL: 'http://example.com/api',
+      params: {
+        apiKey: 'abc',
+      },
+    });
+
+    const uri = client.getUri({
+      url: '/users',
+      params: {
+        page: 2,
+      },
+    });
+
+    expect(uri).to.equal('http://example.com/api/users?apiKey=abc&page=2');
+  });
+});

tests/smoke/cjs/tests/interceptors.smoke.test.cjs

@@ -0,0 +1,149 @@
+const { EventEmitter } = require('events');
+const { PassThrough } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const createTransport = (responseBody) => {
+  const calls = [];
+
+  const transport = {
+    request(options, onResponse) {
+      calls.push(options);
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+      req.end = () => {
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end(responseBody || '{"value":"ok"}');
+      };
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCalls: () => calls,
+  };
+};
+
+describe('interceptors compat (dist export only)', () => {
+  it('applies request interceptors before dispatch', async () => {
+    const { transport, getCalls } = createTransport();
+    const client = axios.create();
+
+    client.interceptors.request.use((config) => {
+      config.headers = config.headers || {};
+      config.headers['X-One'] = '1';
+      return config;
+    });
+
+    client.interceptors.request.use((config) => {
+      config.headers['X-Two'] = '2';
+      return config;
+    });
+
+    await client.get('http://example.com/resource', {
+      transport,
+      proxy: false,
+    });
+
+    expect(getCalls()).to.have.lengthOf(1);
+    expect(getCalls()[0].headers['X-One']).to.equal('1');
+    expect(getCalls()[0].headers['X-Two']).to.equal('2');
+  });
+
+  it('applies response interceptors in registration order', async () => {
+    const { transport } = createTransport('{"n":1}');
+    const client = axios.create();
+
+    client.interceptors.response.use((response) => {
+      response.data.n += 1;
+      return response;
+    });
+
+    client.interceptors.response.use((response) => {
+      response.data.n *= 10;
+      return response;
+    });
+
+    const response = await client.get('http://example.com/resource', {
+      transport,
+      proxy: false,
+    });
+
+    expect(response.data.n).to.equal(20);
+  });
+
+  it('supports ejecting request interceptors', async () => {
+    const { transport, getCalls } = createTransport();
+    const client = axios.create();
+
+    const id = client.interceptors.request.use((config) => {
+      config.headers = config.headers || {};
+      config.headers['X-Ejected'] = 'yes';
+      return config;
+    });
+
+    client.interceptors.request.eject(id);
+
+    await client.get('http://example.com/resource', {
+      transport,
+      proxy: false,
+    });
+
+    expect(getCalls()).to.have.lengthOf(1);
+    expect(getCalls()[0].headers['X-Ejected']).to.be.undefined;
+  });
+
+  it('supports async request interceptors', async () => {
+    const { transport, getCalls } = createTransport();
+    const client = axios.create();
+
+    client.interceptors.request.use(async (config) => {
+      await Promise.resolve();
+      config.headers = config.headers || {};
+      config.headers['X-Async'] = 'true';
+      return config;
+    });
+
+    await client.get('http://example.com/resource', {
+      transport,
+      proxy: false,
+    });
+
+    expect(getCalls()[0].headers['X-Async']).to.equal('true');
+  });
+
+  it('propagates errors thrown by request interceptors', async () => {
+    const { transport, getCalls } = createTransport();
+    const client = axios.create();
+
+    client.interceptors.request.use(() => {
+      throw new Error('blocked-by-interceptor');
+    });
+
+    const err = await client
+      .get('http://example.com/resource', {
+        transport,
+        proxy: false,
+      })
+      .catch((e) => e);
+
+    expect(err).to.be.instanceOf(Error);
+    expect(err.message).to.contain('blocked-by-interceptor');
+    expect(getCalls()).to.have.lengthOf(0);
+  });
+});

tests/smoke/cjs/tests/progress.smoke.test.cjs

@@ -0,0 +1,113 @@
+const { Readable, Writable, PassThrough } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const createProgressTransport = (config) => {
+  const opts = config || {};
+  const responseChunks = opts.responseChunks || ['ok'];
+  const responseHeaders = opts.responseHeaders || {};
+
+  return {
+    request(_options, onResponse) {
+      const req = new Writable({
+        write(_chunk, _encoding, callback) {
+          callback();
+        },
+      });
+
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.close = () => {
+        req.destroyed = true;
+      };
+
+      const originalDestroy = req.destroy.bind(req);
+      req.destroy = (...args) => {
+        req.destroyed = true;
+        return originalDestroy(...args);
+      };
+
+      const originalEnd = req.end.bind(req);
+      req.end = (...args) => {
+        originalEnd(...args);
+
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = Object.assign(
+          {
+            'content-type': 'text/plain',
+          },
+          responseHeaders
+        );
+        res.req = req;
+
+        onResponse(res);
+
+        responseChunks.forEach((chunk) => {
+          res.write(chunk);
+        });
+        res.end();
+      };
+
+      return req;
+    },
+  };
+};
+
+describe('progress compat (dist export only)', () => {
+  it('emits upload progress events for stream payloads', async () => {
+    const samples = [];
+    const payload = ['abc', 'def', 'ghi'];
+    const total = payload.join('').length;
+
+    await axios.post('http://example.com/upload', Readable.from(payload), {
+      proxy: false,
+      headers: {
+        'Content-Length': String(total),
+      },
+      onUploadProgress: ({ loaded, total: reportedTotal, upload }) => {
+        samples.push({ loaded, total: reportedTotal, upload });
+      },
+      transport: createProgressTransport({
+        responseChunks: ['uploaded'],
+      }),
+    });
+
+    expect(samples.length).to.be.greaterThan(0);
+    expect(samples[samples.length - 1]).to.deep.include({
+      loaded: total,
+      total,
+      upload: true,
+    });
+  });
+
+  it('emits download progress events', async () => {
+    const samples = [];
+    const chunks = ['ab', 'cd', 'ef'];
+    const total = chunks.join('').length;
+
+    const response = await axios.get('http://example.com/download', {
+      proxy: false,
+      responseType: 'text',
+      onDownloadProgress: ({ loaded, total: reportedTotal, download }) => {
+        samples.push({ loaded, total: reportedTotal, download });
+      },
+      transport: createProgressTransport({
+        responseChunks: chunks,
+        responseHeaders: {
+          'content-length': String(total),
+        },
+      }),
+    });
+
+    expect(response.data).to.equal('abcdef');
+    expect(samples.length).to.be.greaterThan(0);
+    expect(samples[samples.length - 1]).to.deep.include({
+      loaded: total,
+      total,
+      download: true,
+    });
+  });
+});

tests/smoke/cjs/tests/rateLimit.smoke.test.cjs

@@ -0,0 +1,105 @@
+const { EventEmitter } = require('events');
+const { PassThrough } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const createTransportCapture = () => {
+  let capturedOptions;
+
+  const transport = {
+    request(options, onResponse) {
+      capturedOptions = options;
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+      req.end = () => {
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end('{"ok":true}');
+      };
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCapturedOptions: () => capturedOptions,
+  };
+};
+
+describe('rateLimit compat (dist export only)', () => {
+  it('accepts numeric maxRate config', async () => {
+    const response = await axios.get('http://example.com/rate', {
+      maxRate: 1024,
+      adapter: async (config) => ({
+        data: { maxRate: config.maxRate },
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data.maxRate).to.equal(1024);
+  });
+
+  it('accepts tuple maxRate config [upload, download]', async () => {
+    const response = await axios.get('http://example.com/rate', {
+      maxRate: [2048, 4096],
+      adapter: async (config) => ({
+        data: { maxRate: config.maxRate },
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data.maxRate).to.deep.equal([2048, 4096]);
+  });
+
+  it('merges instance and request maxRate values', async () => {
+    const client = axios.create({
+      maxRate: [1000, 2000],
+    });
+
+    const response = await client.get('http://example.com/rate', {
+      maxRate: [3000, 4000],
+      adapter: async (config) => ({
+        data: { maxRate: config.maxRate },
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data.maxRate).to.deep.equal([3000, 4000]);
+  });
+
+  it('supports maxRate in node transport flow without errors', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    const response = await axios.get('http://example.com/rate', {
+      proxy: false,
+      maxRate: [1500, 2500],
+      transport,
+    });
+
+    expect(response.status).to.equal(200);
+    expect(getCapturedOptions().method).to.equal('GET');
+    expect(getCapturedOptions().path).to.equal('/rate');
+  });
+});

tests/smoke/cjs/tests/timeout.smoke.test.cjs

@@ -0,0 +1,116 @@
+const { EventEmitter } = require('events');
+const { PassThrough } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const createTransport = (config) => {
+  const opts = config || {};
+
+  return {
+    request(_options, onResponse) {
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req._timeoutCallback = null;
+
+      req.setTimeout = (_ms, callback) => {
+        req._timeoutCallback = callback;
+      };
+
+      req.write = () => true;
+
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+
+      req.end = () => {
+        if (opts.triggerTimeout && req._timeoutCallback) {
+          req._timeoutCallback();
+          return;
+        }
+
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+
+        onResponse(res);
+        res.end(opts.body || '{"ok":true}');
+      };
+
+      return req;
+    },
+  };
+};
+
+describe('timeout compat (dist export only)', () => {
+  it('rejects with ECONNABORTED on timeout', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: 25,
+        transport: createTransport({ triggerTimeout: true }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).to.equal(true);
+    expect(err.code).to.equal('ECONNABORTED');
+    expect(err.message).to.equal('timeout of 25ms exceeded');
+  });
+
+  it('uses timeoutErrorMessage when provided', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: 25,
+        timeoutErrorMessage: 'custom timeout',
+        transport: createTransport({ triggerTimeout: true }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).to.equal(true);
+    expect(err.code).to.equal('ECONNABORTED');
+    expect(err.message).to.equal('custom timeout');
+  });
+
+  it('accepts timeout as a numeric string', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: '30',
+        transport: createTransport({ triggerTimeout: true }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).to.equal(true);
+    expect(err.code).to.equal('ECONNABORTED');
+    expect(err.message).to.equal('timeout of 30ms exceeded');
+  });
+
+  it('rejects with ERR_BAD_OPTION_VALUE when timeout is not parsable', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: { invalid: true },
+        transport: createTransport(),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).to.equal(true);
+    expect(err.code).to.equal('ERR_BAD_OPTION_VALUE');
+    expect(err.message).to.equal('error trying to parse `config.timeout` to int');
+  });
+
+  it('does not time out when timeout is 0', async () => {
+    const response = await axios.get('http://example.com/no-timeout', {
+      proxy: false,
+      timeout: 0,
+      transport: createTransport({ body: '{"ok":true}' }),
+    });
+
+    expect(response.status).to.equal(200);
+    expect(response.data).to.deep.equal({ ok: true });
+  });
+});

tests/smoke/cjs/tests/urlencode.smoke.test.cjs

@@ -0,0 +1,146 @@
+const { EventEmitter } = require('events');
+const { PassThrough } = require('stream');
+const axios = require('axios');
+const { describe, it } = require('mocha');
+const { expect } = require('chai');
+
+const createEchoTransport = () => {
+  let capturedOptions;
+
+  const transport = {
+    request(options, onResponse) {
+      capturedOptions = options;
+      const chunks = [];
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+      req.write = (chunk) => {
+        chunks.push(Buffer.from(chunk));
+        return true;
+      };
+      req.end = (chunk) => {
+        if (chunk) {
+          chunks.push(Buffer.from(chunk));
+        }
+
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end(
+          JSON.stringify({
+            path: options.path,
+            body: Buffer.concat(chunks).toString('utf8'),
+            contentType:
+              options.headers &&
+              (options.headers['Content-Type'] || options.headers['content-type']),
+          })
+        );
+      };
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCapturedOptions: () => capturedOptions,
+  };
+};
+
+describe('urlencode compat (dist export only)', () => {
+  it('serializes params into request URL', async () => {
+    const { transport } = createEchoTransport();
+
+    const response = await axios.get('http://example.com/search', {
+      proxy: false,
+      transport,
+      params: {
+        q: 'axios docs',
+        page: 2,
+      },
+    });
+
+    expect(response.data.path).to.equal('/search?q=axios+docs&page=2');
+  });
+
+  it('supports custom paramsSerializer function', async () => {
+    const { transport } = createEchoTransport();
+
+    const response = await axios.get('http://example.com/search', {
+      proxy: false,
+      transport,
+      params: { q: 'ignored' },
+      paramsSerializer: () => 'fixed=1',
+    });
+
+    expect(response.data.path).to.equal('/search?fixed=1');
+  });
+
+  it('supports URLSearchParams payloads', async () => {
+    const { transport } = createEchoTransport();
+    const payload = new URLSearchParams();
+    payload.append('name', 'axios');
+    payload.append('mode', 'compat');
+
+    const response = await axios.post('http://example.com/form', payload, {
+      proxy: false,
+      transport,
+    });
+
+    expect(response.data.body).to.equal('name=axios&mode=compat');
+    expect(response.data.contentType).to.contain('application/x-www-form-urlencoded');
+  });
+
+  it('serializes object payload when content-type is application/x-www-form-urlencoded', async () => {
+    const { transport } = createEchoTransport();
+
+    const response = await axios.post(
+      'http://example.com/form',
+      {
+        name: 'axios',
+        mode: 'compat',
+      },
+      {
+        proxy: false,
+        transport,
+        headers: {
+          'content-type': 'application/x-www-form-urlencoded',
+        },
+      }
+    );
+
+    expect(response.data.body).to.equal('name=axios&mode=compat');
+    expect(response.data.contentType).to.contain('application/x-www-form-urlencoded');
+  });
+
+  it('respects formSerializer options for index formatting', async () => {
+    const { transport } = createEchoTransport();
+
+    const response = await axios.post(
+      'http://example.com/form',
+      {
+        arr: ['1', '2'],
+      },
+      {
+        proxy: false,
+        transport,
+        headers: {
+          'content-type': 'application/x-www-form-urlencoded',
+        },
+        formSerializer: {
+          indexes: true,
+        },
+      }
+    );
+
+    expect(response.data.body).to.equal('arr%5B0%5D=1&arr%5B1%5D=2');
+  });
+});

tests/smoke/esm/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "@axios/esm-smoke-tests",
+  "version": "1.0.0",
+  "description": "ESM smoke tests for axios",
+  "private": true,
+  "scripts": {
+    "test:smoke:esm:vitest": "vitest run --config vitest.config.js --project smoke"
+  },
+  "keywords": [],
+  "author": "axios team",
+  "license": "MIT",
+  "dependencies": {
+    "axios": "file:../../../"
+  },
+  "devDependencies": {
+    "vitest": "4.0.18"
+  }
+}

tests/smoke/esm/tests/auth.smoke.test.js

@@ -0,0 +1,137 @@
+import { afterEach, describe, expect, it } from 'vitest';
+
+import http from 'http';
+import axios from 'axios';
+
+const startServer = (handler) => {
+  return new Promise((resolve) => {
+    const server = http.createServer(handler);
+
+    server.listen(0, '127.0.0.1', () => {
+      resolve(server);
+    });
+  });
+};
+
+const stopServer = (server) => {
+  if (!server || !server.listening) {
+    return Promise.resolve();
+  }
+
+  return new Promise((resolve, reject) => {
+    server.close((error) => {
+      if (error) {
+        reject(error);
+        return;
+      }
+      resolve();
+    });
+  });
+};
+
+describe('auth compat (dist export only)', () => {
+  let server;
+
+  afterEach(async () => {
+    await stopServer(server);
+    server = undefined;
+  });
+
+  const requestWithConfig = async (config) => {
+    server = await startServer((req, res) => {
+      res.setHeader('Content-Type', 'text/plain');
+      res.end(req.headers.authorization || '');
+    });
+
+    const { port } = server.address();
+
+    return axios.get(
+      `http://127.0.0.1:${port}/`,
+      Object.assign(
+        {
+          proxy: false,
+        },
+        config || {}
+      )
+    );
+  };
+
+  it('sets Basic Authorization header from auth credentials', async () => {
+    const response = await requestWithConfig({
+      auth: {
+        username: 'janedoe',
+        password: 's00pers3cret',
+      },
+    });
+
+    const expected = `Basic ${Buffer.from('janedoe:s00pers3cret', 'utf8').toString('base64')}`;
+
+    expect(response.data).toBe(expected);
+  });
+
+  it('supports auth without password', async () => {
+    const response = await requestWithConfig({
+      auth: {
+        username: 'Aladdin',
+      },
+    });
+
+    const expected = `Basic ${Buffer.from('Aladdin:', 'utf8').toString('base64')}`;
+
+    expect(response.data).toBe(expected);
+  });
+
+  it('overwrites an existing Authorization header when auth is provided', async () => {
+    const response = await requestWithConfig({
+      headers: {
+        Authorization: 'Bearer token-123',
+      },
+      auth: {
+        username: 'foo',
+        password: 'bar',
+      },
+    });
+
+    const expected = `Basic ${Buffer.from('foo:bar', 'utf8').toString('base64')}`;
+
+    expect(response.data).toBe(expected);
+  });
+
+  it('uses URL credentials when auth config is not provided (node adapter behavior)', async () => {
+    server = await startServer((req, res) => {
+      res.setHeader('Content-Type', 'text/plain');
+      res.end(req.headers.authorization || '');
+    });
+
+    const { port } = server.address();
+
+    const response = await axios.get(`http://urluser:urlpass@127.0.0.1:${port}/`, {
+      proxy: false,
+    });
+
+    const expected = `Basic ${Buffer.from('urluser:urlpass', 'utf8').toString('base64')}`;
+
+    expect(response.data).toBe(expected);
+  });
+
+  it('prefers auth config over URL credentials', async () => {
+    server = await startServer((req, res) => {
+      res.setHeader('Content-Type', 'text/plain');
+      res.end(req.headers.authorization || '');
+    });
+
+    const { port } = server.address();
+
+    const response = await axios.get(`http://urluser:urlpass@127.0.0.1:${port}/`, {
+      proxy: false,
+      auth: {
+        username: 'configuser',
+        password: 'configpass',
+      },
+    });
+
+    const expected = `Basic ${Buffer.from('configuser:configpass', 'utf8').toString('base64')}`;
+
+    expect(response.data).toBe(expected);
+  });
+});

tests/smoke/esm/tests/basic.smoke.test.js

@@ -0,0 +1,145 @@
+import { describe, expect, it } from 'vitest';
+
+import { EventEmitter } from 'events';
+import { PassThrough } from 'stream';
+import axios from 'axios';
+
+const createTransportCapture = () => {
+  let capturedOptions;
+
+  const transport = {
+    request(options, onResponse) {
+      capturedOptions = options;
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.end = () => {
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end('{"ok":true}');
+      };
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCapturedOptions: () => capturedOptions,
+  };
+};
+
+const runRequest = async (run) => {
+  const { transport, getCapturedOptions } = createTransportCapture();
+  await run(transport);
+
+  return getCapturedOptions();
+};
+
+describe('basic compat (dist export only)', () => {
+  it('supports the simplest axios(url) request pattern', async () => {
+    const options = await runRequest((transport) =>
+      axios('http://example.com/users', {
+        transport,
+        proxy: false,
+      })
+    );
+
+    expect(options.method).toBe('GET');
+    expect(options.path).toBe('/users');
+  });
+
+  it('supports get()', async () => {
+    const options = await runRequest((transport) =>
+      axios.get('http://example.com/items?limit=10', { transport, proxy: false })
+    );
+
+    expect(options.method).toBe('GET');
+    expect(options.path).toBe('/items?limit=10');
+  });
+
+  it('supports delete()', async () => {
+    const options = await runRequest((transport) =>
+      axios.delete('http://example.com/items/1', { transport, proxy: false })
+    );
+
+    expect(options.method).toBe('DELETE');
+    expect(options.path).toBe('/items/1');
+  });
+
+  it('supports head()', async () => {
+    const options = await runRequest((transport) =>
+      axios.head('http://example.com/health', { transport, proxy: false })
+    );
+
+    expect(options.method).toBe('HEAD');
+    expect(options.path).toBe('/health');
+  });
+
+  it('supports options()', async () => {
+    const options = await runRequest((transport) =>
+      axios.options('http://example.com/items', { transport, proxy: false })
+    );
+
+    expect(options.method).toBe('OPTIONS');
+    expect(options.path).toBe('/items');
+  });
+
+  it('supports post()', async () => {
+    const options = await runRequest((transport) =>
+      axios.post(
+        'http://example.com/items',
+        { name: 'widget' },
+        {
+          transport,
+          proxy: false,
+        }
+      )
+    );
+
+    expect(options.method).toBe('POST');
+    expect(options.path).toBe('/items');
+  });
+
+  it('supports put()', async () => {
+    const options = await runRequest((transport) =>
+      axios.put(
+        'http://example.com/items/1',
+        { name: 'updated-widget' },
+        {
+          transport,
+          proxy: false,
+        }
+      )
+    );
+
+    expect(options.method).toBe('PUT');
+    expect(options.path).toBe('/items/1');
+  });
+
+  it('supports patch()', async () => {
+    const options = await runRequest((transport) =>
+      axios.patch(
+        'http://example.com/items/1',
+        { status: 'active' },
+        {
+          transport,
+          proxy: false,
+        }
+      )
+    );
+
+    expect(options.method).toBe('PATCH');
+    expect(options.path).toBe('/items/1');
+  });
+});

tests/smoke/esm/tests/cancel.smoke.test.js

@@ -0,0 +1,111 @@
+import { describe, expect, it } from 'vitest';
+
+import { EventEmitter } from 'events';
+import axios from 'axios';
+
+const createPendingTransport = () => {
+  let requestCount = 0;
+
+  const transport = {
+    request() {
+      requestCount += 1;
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.end = () => {};
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getRequestCount: () => requestCount,
+  };
+};
+
+describe('cancel compat (dist export only)', () => {
+  it('supports cancellation with AbortController (pre-aborted signal)', async () => {
+    const { transport, getRequestCount } = createPendingTransport();
+    const controller = new AbortController();
+    controller.abort();
+
+    try {
+      const request = axios.get('http://example.com/resource', {
+        signal: controller.signal,
+        transport,
+        proxy: false,
+      });
+
+      controller.abort();
+      await request;
+    } catch (error) {
+      expect(error.code).toBe('ERR_CANCELED');
+    }
+
+    expect(getRequestCount()).toBe(0);
+  });
+
+  it('supports cancellation with AbortController (in-flight)', async () => {
+    const { transport, getRequestCount } = createPendingTransport();
+    const controller = new AbortController();
+
+    try {
+      const request = axios.get('http://example.com/resource', {
+        signal: controller.signal,
+        transport,
+        proxy: false,
+      });
+
+      controller.abort();
+      await request;
+    } catch (error) {
+      expect(error.code).toBe('ERR_CANCELED');
+    }
+
+    expect(getRequestCount()).toBe(1);
+  });
+
+  it('supports cancellation with CancelToken (pre-canceled token)', async () => {
+    const { transport, getRequestCount } = createPendingTransport();
+    const source = axios.CancelToken.source();
+    source.cancel('Operation canceled by the user.');
+
+    const error = await axios
+      .get('http://example.com/resource', {
+        cancelToken: source.token,
+        transport,
+        proxy: false,
+      })
+      .catch((err) => err);
+
+    expect(axios.isCancel(error)).toBe(true);
+    expect(error.code).toBe('ERR_CANCELED');
+    expect(getRequestCount()).toBe(0);
+  });
+
+  it('supports cancellation with CancelToken (in-flight)', async () => {
+    const { transport, getRequestCount } = createPendingTransport();
+    const source = axios.CancelToken.source();
+
+    const request = axios.get('http://example.com/resource', {
+      cancelToken: source.token,
+      transport,
+      proxy: false,
+    });
+
+    source.cancel('Operation canceled by the user.');
+
+    const error = await request.catch((err) => err);
+
+    expect(axios.isCancel(error)).toBe(true);
+    expect(error.code).toBe('ERR_CANCELED');
+    expect(getRequestCount()).toBe(1);
+  });
+});

tests/smoke/esm/tests/error.smoke.test.js

@@ -0,0 +1,139 @@
+import { describe, expect, it } from 'vitest';
+
+import { EventEmitter } from 'events';
+import { PassThrough } from 'stream';
+import axios from 'axios';
+
+const createTransport = (config) => {
+  const opts = config || {};
+
+  return {
+    request(options, onResponse) {
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.write = () => true;
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+
+      req.setTimeout = (_ms, cb) => {
+        if (opts.timeout) {
+          req._timeoutCallback = cb;
+        }
+      };
+
+      req.end = () => {
+        if (opts.error) {
+          req.emit('error', opts.error);
+          return;
+        }
+
+        if (opts.timeout && req._timeoutCallback) {
+          req._timeoutCallback();
+          return;
+        }
+
+        const res = new PassThrough();
+        res.statusCode =
+          opts.response && opts.response.statusCode !== undefined ? opts.response.statusCode : 200;
+        res.statusMessage =
+          opts.response && opts.response.statusMessage ? opts.response.statusMessage : 'OK';
+        res.headers =
+          opts.response && opts.response.headers
+            ? opts.response.headers
+            : { 'content-type': 'application/json' };
+        res.req = req;
+
+        onResponse(res);
+        res.end(
+          opts.response && opts.response.body !== undefined ? opts.response.body : '{"ok":true}'
+        );
+      };
+
+      return req;
+    },
+  };
+};
+
+describe('error compat (dist export only)', () => {
+  it('rejects with AxiosError for non-2xx responses by default', async () => {
+    const err = await axios
+      .get('http://example.com/fail', {
+        proxy: false,
+        transport: createTransport({
+          response: {
+            statusCode: 500,
+            statusMessage: 'Internal Server Error',
+            body: '{"error":"boom"}',
+          },
+        }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).toBe(true);
+    expect(err.response.status).toBe(500);
+    expect(err.message).toContain('500');
+  });
+
+  it('resolves when validateStatus allows non-2xx responses', async () => {
+    const response = await axios.get('http://example.com/allowed', {
+      proxy: false,
+      validateStatus: () => true,
+      transport: createTransport({
+        response: {
+          statusCode: 500,
+          statusMessage: 'Internal Server Error',
+          body: '{"ok":false}',
+        },
+      }),
+    });
+
+    expect(response.status).toBe(500);
+    expect(response.data).toEqual({ ok: false });
+  });
+
+  it('wraps transport errors as AxiosError', async () => {
+    const err = await axios
+      .get('http://example.com/network', {
+        proxy: false,
+        transport: createTransport({
+          error: new Error('socket hang up'),
+        }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).toBe(true);
+    expect(err.message).toContain('socket hang up');
+    expect(err.toJSON).toBeTypeOf('function');
+  });
+
+  it('rejects with ECONNABORTED on timeout', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: 10,
+        transport: createTransport({ timeout: true }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).toBe(true);
+    expect(err.code).toBe('ECONNABORTED');
+    expect(err.message).toBe('timeout of 10ms exceeded');
+  });
+
+  it('uses timeoutErrorMessage when provided', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: 25,
+        timeoutErrorMessage: 'custom timeout message',
+        transport: createTransport({ timeout: true }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).toBe(true);
+    expect(err.code).toBe('ECONNABORTED');
+    expect(err.message).toBe('custom timeout message');
+  });
+});

tests/smoke/esm/tests/fetch.smoke.test.js

@@ -0,0 +1,142 @@
+import { describe, expect, it } from 'vitest';
+
+import axios from 'axios';
+
+const createFetchMock = (responseFactory) => {
+  const calls = [];
+
+  const mockFetch = async (input, init) => {
+    calls.push({ input, init: init || {} });
+
+    if (responseFactory) {
+      return responseFactory(input, init || {});
+    }
+
+    return new Response(JSON.stringify({ ok: true }), {
+      status: 200,
+      headers: { 'Content-Type': 'application/json' },
+    });
+  };
+
+  return {
+    mockFetch,
+    getCalls: () => calls,
+  };
+};
+
+describe('fetch compat (dist export only)', () => {
+  it('uses fetch adapter and resolves JSON response', async () => {
+    const { mockFetch, getCalls } = createFetchMock();
+
+    const response = await axios.get('https://example.com/users', {
+      adapter: 'fetch',
+      env: {
+        fetch: mockFetch,
+        Request,
+        Response,
+      },
+    });
+
+    expect(response.data).toEqual({ ok: true });
+    expect(response.status).toBe(200);
+    expect(getCalls()).toHaveLength(1);
+  });
+
+  it('sends method, headers and body for post requests', async () => {
+    const { mockFetch, getCalls } = createFetchMock(async (input, init) => {
+      const requestInit = init || {};
+      const isRequest = input && typeof input !== 'string';
+      const method = isRequest ? input.method : requestInit.method;
+
+      const body =
+        isRequest && typeof input.clone === 'function'
+          ? await input.clone().text()
+          : requestInit.body;
+
+      let contentType;
+      if (isRequest && input.headers) {
+        contentType = input.headers.get('content-type');
+      } else if (requestInit.headers) {
+        contentType = requestInit.headers['Content-Type'] || requestInit.headers['content-type'];
+      }
+
+      return new Response(
+        JSON.stringify({
+          url: typeof input === 'string' ? input : input.url,
+          method,
+          contentType,
+          body,
+        }),
+        {
+          status: 200,
+          headers: { 'Content-Type': 'application/json' },
+        }
+      );
+    });
+
+    const response = await axios.post(
+      'https://example.com/items',
+      { name: 'widget' },
+      {
+        adapter: 'fetch',
+        env: {
+          fetch: mockFetch,
+          Request,
+          Response,
+        },
+      }
+    );
+
+    expect(getCalls()).toHaveLength(1);
+    expect(response.data.url).toBe('https://example.com/items');
+    expect(response.data.method).toBe('POST');
+    expect(response.data.contentType).toContain('application/json');
+    expect(response.data.body).toBe(JSON.stringify({ name: 'widget' }));
+  });
+
+  it('rejects non-2xx fetch responses by default', async () => {
+    const { mockFetch } = createFetchMock(
+      () =>
+        new Response(JSON.stringify({ error: 'boom' }), {
+          status: 500,
+          statusText: 'Internal Server Error',
+          headers: { 'Content-Type': 'application/json' },
+        })
+    );
+
+    const err = await axios
+      .get('https://example.com/fail', {
+        adapter: 'fetch',
+        env: {
+          fetch: mockFetch,
+          Request,
+          Response,
+        },
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).toBe(true);
+    expect(err.response.status).toBe(500);
+  });
+
+  it('supports cancellation with AbortController in fetch mode', async () => {
+    const { mockFetch } = createFetchMock();
+    const controller = new AbortController();
+    controller.abort();
+
+    const err = await axios
+      .get('https://example.com/cancel', {
+        adapter: 'fetch',
+        signal: controller.signal,
+        env: {
+          fetch: mockFetch,
+          Request,
+          Response,
+        },
+      })
+      .catch((e) => e);
+
+    expect(axios.isCancel(err)).toBe(true);
+    expect(err.code).toBe('ERR_CANCELED');
+  });
+});

tests/smoke/esm/tests/files.smoke.test.js

@@ -0,0 +1,115 @@
+import { describe, expect, it } from 'vitest';
+
+import { PassThrough, Readable, Writable } from 'stream';
+import axios from 'axios';
+
+const createCaptureTransport = (buildResponse) => {
+  return {
+    request(options, onResponse) {
+      const chunks = [];
+
+      const req = new Writable({
+        write(chunk, _encoding, callback) {
+          chunks.push(Buffer.from(chunk));
+          callback();
+        },
+      });
+
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.close = () => {
+        req.destroyed = true;
+      };
+
+      const originalDestroy = req.destroy.bind(req);
+      req.destroy = (...args) => {
+        req.destroyed = true;
+        return originalDestroy(...args);
+      };
+
+      const originalEnd = req.end.bind(req);
+      req.end = (...args) => {
+        originalEnd(...args);
+
+        const body = Buffer.concat(chunks);
+        const response = buildResponse ? buildResponse(body, options) : {};
+
+        const res = new PassThrough();
+        res.statusCode = response.statusCode !== undefined ? response.statusCode : 200;
+        res.statusMessage = response.statusMessage || 'OK';
+        res.headers = response.headers || { 'content-type': 'application/json' };
+        res.req = req;
+
+        onResponse(res);
+        res.end(response.body || JSON.stringify({ size: body.length }));
+      };
+
+      req.on('error', () => {});
+      return req;
+    },
+  };
+};
+
+describe('files compat (dist export only)', () => {
+  it('supports posting Buffer payloads', async () => {
+    const source = Buffer.from('binary-\x00-data', 'utf8');
+
+    const response = await axios.post('http://example.com/upload', source, {
+      proxy: false,
+      transport: createCaptureTransport((body) => ({
+        body: JSON.stringify({ echoed: body.toString('base64') }),
+      })),
+    });
+
+    expect(response.data.echoed).toBe(source.toString('base64'));
+  });
+
+  it('supports posting Uint8Array payloads', async () => {
+    const source = Uint8Array.from([1, 2, 3, 4, 255]);
+
+    const response = await axios.post('http://example.com/upload', source, {
+      proxy: false,
+      transport: createCaptureTransport((body) => ({
+        body: JSON.stringify({ echoed: Array.from(body.values()) }),
+      })),
+    });
+
+    expect(response.data.echoed).toEqual([1, 2, 3, 4, 255]);
+  });
+
+  it('supports posting Readable stream payloads', async () => {
+    const streamData = ['hello ', 'stream ', 'world'];
+    const source = Readable.from(streamData);
+
+    const response = await axios.post('http://example.com/upload', source, {
+      proxy: false,
+      headers: { 'Content-Type': 'application/octet-stream' },
+      transport: createCaptureTransport((body, options) => ({
+        body: JSON.stringify({
+          text: body.toString('utf8'),
+          contentType:
+            options.headers && (options.headers['Content-Type'] || options.headers['content-type']),
+        }),
+      })),
+    });
+
+    expect(response.data.text).toBe('hello stream world');
+    expect(response.data.contentType).toContain('application/octet-stream');
+  });
+
+  it('supports binary downloads with responseType=arraybuffer', async () => {
+    const binary = Buffer.from([0xde, 0xad, 0xbe, 0xef]);
+
+    const response = await axios.get('http://example.com/file.bin', {
+      proxy: false,
+      responseType: 'arraybuffer',
+      transport: createCaptureTransport(() => ({
+        headers: { 'content-type': 'application/octet-stream' },
+        body: binary,
+      })),
+    });
+
+    expect(Buffer.isBuffer(response.data)).toBe(true);
+    expect(response.data.equals(binary)).toBe(true);
+  });
+});

tests/smoke/esm/tests/formData.smoke.test.js

@@ -0,0 +1,107 @@
+import { describe, expect, it } from 'vitest';
+
+import { Writable, PassThrough } from 'stream';
+import axios from 'axios';
+
+const createCaptureTransport = (buildResponse) => {
+  return {
+    request(options, onResponse) {
+      const chunks = [];
+
+      const req = new Writable({
+        write(chunk, _encoding, callback) {
+          chunks.push(Buffer.from(chunk));
+          callback();
+        },
+      });
+
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = req.write.bind(req);
+      req.close = () => {
+        req.destroyed = true;
+      };
+
+      const originalDestroy = req.destroy.bind(req);
+      req.destroy = (...args) => {
+        req.destroyed = true;
+        return originalDestroy(...args);
+      };
+
+      const originalEnd = req.end.bind(req);
+      req.end = (...args) => {
+        originalEnd(...args);
+
+        const body = Buffer.concat(chunks);
+        const response = buildResponse ? buildResponse(body, options) : {};
+
+        const res = new PassThrough();
+        res.statusCode = response.statusCode !== undefined ? response.statusCode : 200;
+        res.statusMessage = response.statusMessage || 'OK';
+        res.headers = response.headers || { 'content-type': 'application/json' };
+        res.req = req;
+
+        onResponse(res);
+        res.end(response.body || JSON.stringify({ ok: true }));
+      };
+
+      return req;
+    },
+  };
+};
+
+const bodyAsUtf8 = (value) => {
+  return Buffer.isBuffer(value) ? value.toString('utf8') : String(value);
+};
+
+describe('formData compat (dist export only)', () => {
+  it('supports posting FormData instances', async () => {
+    const form = new FormData();
+    form.append('username', 'janedoe');
+    form.append('role', 'admin');
+
+    const response = await axios.post('http://example.com/form', form, {
+      proxy: false,
+      transport: createCaptureTransport((body, options) => ({
+        body: JSON.stringify({
+          contentType:
+            options.headers && (options.headers['Content-Type'] || options.headers['content-type']),
+          payload: bodyAsUtf8(body),
+        }),
+      })),
+    });
+
+    expect(response.data.contentType).toContain('multipart/form-data');
+    expect(response.data.payload).toContain('name="username"');
+    expect(response.data.payload).toContain('janedoe');
+    expect(response.data.payload).toContain('name="role"');
+    expect(response.data.payload).toContain('admin');
+  });
+
+  it('supports axios.postForm helper', async () => {
+    const response = await axios.postForm(
+      'http://example.com/post-form',
+      {
+        project: 'axios',
+        mode: 'compat',
+      },
+      {
+        proxy: false,
+        transport: createCaptureTransport((body, options) => ({
+          body: JSON.stringify({
+            contentType:
+              options.headers &&
+              (options.headers['Content-Type'] || options.headers['content-type']),
+            payload: bodyAsUtf8(body),
+          }),
+        })),
+      }
+    );
+
+    expect(response.data.contentType).toContain('multipart/form-data');
+    expect(response.data.payload).toContain('name="project"');
+    expect(response.data.payload).toContain('axios');
+    expect(response.data.payload).toContain('name="mode"');
+    expect(response.data.payload).toContain('compat');
+  });
+});

tests/smoke/esm/tests/headers.smoke.test.js

@@ -0,0 +1,125 @@
+import { describe, expect, it } from 'vitest';
+
+import { EventEmitter } from 'events';
+import { PassThrough } from 'stream';
+import axios from 'axios';
+
+const normalizeHeaders = (headers) => {
+  const result = {};
+
+  Object.entries(headers || {}).forEach(([key, value]) => {
+    result[key.toLowerCase()] = value;
+  });
+
+  return result;
+};
+
+const createTransportCapture = () => {
+  let capturedOptions;
+
+  const transport = {
+    request(options, onResponse) {
+      capturedOptions = options;
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+      req.end = () => {
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end('{"ok":true}');
+      };
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCapturedOptions: () => capturedOptions,
+  };
+};
+
+describe('headers compat (dist export only)', () => {
+  it('sends default Accept header', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    await axios.get('http://example.com/default-headers', {
+      transport,
+      proxy: false,
+    });
+
+    const headers = normalizeHeaders(getCapturedOptions().headers);
+    expect(headers.accept).toBe('application/json, text/plain, */*');
+  });
+
+  it('supports custom headers', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    await axios.get('http://example.com/custom-headers', {
+      transport,
+      proxy: false,
+      headers: {
+        'X-Trace-Id': 'trace-123',
+        Authorization: 'Bearer token-abc',
+      },
+    });
+
+    const headers = normalizeHeaders(getCapturedOptions().headers);
+    expect(headers['x-trace-id']).toBe('trace-123');
+    expect(headers.authorization).toBe('Bearer token-abc');
+  });
+
+  it('treats header names as case-insensitive when overriding', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    await axios.get('http://example.com/case-insensitive', {
+      transport,
+      proxy: false,
+      headers: {
+        authorization: 'Bearer old-token',
+        AuThOrIzAtIoN: 'Bearer new-token',
+      },
+    });
+
+    const headers = normalizeHeaders(getCapturedOptions().headers);
+    expect(headers.authorization).toBe('Bearer new-token');
+  });
+
+  it('sets content-type for json post payloads', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    await axios.post(
+      'http://example.com/post-json',
+      { name: 'widget' },
+      {
+        transport,
+        proxy: false,
+      }
+    );
+
+    const headers = normalizeHeaders(getCapturedOptions().headers);
+    expect(headers['content-type']).toContain('application/json');
+  });
+
+  it('does not force content-type for get requests without body', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    await axios.get('http://example.com/get-no-body', {
+      transport,
+      proxy: false,
+    });
+
+    const headers = normalizeHeaders(getCapturedOptions().headers);
+    expect(headers['content-type']).toBeUndefined();
+  });
+});

tests/smoke/esm/tests/http2.smoke.test.js

@@ -0,0 +1,86 @@
+import { describe, expect, it } from 'vitest';
+
+import axios from 'axios';
+
+describe('http2 compat (dist export only)', () => {
+  it('keeps instance-level httpVersion and http2Options in request config', async () => {
+    const client = axios.create({
+      baseURL: 'https://example.com',
+      httpVersion: 2,
+      http2Options: {
+        rejectUnauthorized: false,
+      },
+    });
+
+    const response = await client.get('/resource', {
+      adapter: async (config) => ({
+        data: {
+          httpVersion: config.httpVersion,
+          http2Options: config.http2Options,
+        },
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data.httpVersion).toBe(2);
+    expect(response.data.http2Options).toEqual({
+      rejectUnauthorized: false,
+    });
+  });
+
+  it('merges request http2Options with instance http2Options', async () => {
+    const client = axios.create({
+      baseURL: 'https://example.com',
+      httpVersion: 2,
+      http2Options: {
+        rejectUnauthorized: false,
+        sessionTimeout: 1000,
+      },
+    });
+
+    const response = await client.get('/resource', {
+      http2Options: {
+        sessionTimeout: 5000,
+        customFlag: true,
+      },
+      adapter: async (config) => ({
+        data: config.http2Options,
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data).toEqual({
+      rejectUnauthorized: false,
+      sessionTimeout: 5000,
+      customFlag: true,
+    });
+  });
+
+  it('allows request-level httpVersion override', async () => {
+    const client = axios.create({
+      baseURL: 'https://example.com',
+      httpVersion: 2,
+    });
+
+    const response = await client.get('/resource', {
+      httpVersion: 1,
+      adapter: async (config) => ({
+        data: {
+          httpVersion: config.httpVersion,
+        },
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data.httpVersion).toBe(1);
+  });
+});

tests/smoke/esm/tests/instance.smoke.test.js

@@ -0,0 +1,146 @@
+import { describe, expect, it } from 'vitest';
+
+import { EventEmitter } from 'events';
+import { PassThrough } from 'stream';
+import axios from 'axios';
+
+const createTransportCapture = (responseBody) => {
+  const calls = [];
+
+  const transport = {
+    request(options, onResponse) {
+      calls.push(options);
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+      req.end = () => {
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end(responseBody ? responseBody : '{"ok":true}');
+      };
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCalls: () => calls,
+  };
+};
+
+describe('instance compat (dist export only)', () => {
+  it('creates isolated instances with separate defaults', async () => {
+    const { transport, getCalls } = createTransportCapture();
+
+    const clientA = axios.create({
+      baseURL: 'http://example.com/api-a',
+      headers: {
+        'X-App': 'A',
+      },
+    });
+    const clientB = axios.create({
+      baseURL: 'http://example.com/api-b',
+      headers: {
+        'X-App': 'B',
+      },
+    });
+
+    await clientA.get('/users', { transport, proxy: false });
+    await clientB.get('/users', { transport, proxy: false });
+
+    const [callA, callB] = getCalls();
+    expect(callA.path).toBe('/api-a/users');
+    expect(callB.path).toBe('/api-b/users');
+    expect(callA.headers['X-App']).toBe('A');
+    expect(callB.headers['X-App']).toBe('B');
+  });
+
+  it('supports callable instance form instance(config)', async () => {
+    const { transport, getCalls } = createTransportCapture();
+    const client = axios.create({
+      baseURL: 'http://example.com',
+    });
+
+    await client({
+      url: '/status',
+      method: 'get',
+      transport,
+      proxy: false,
+    });
+
+    expect(getCalls()).toHaveLength(1);
+    expect(getCalls()[0].method).toBe('GET');
+    expect(getCalls()[0].path).toBe('/status');
+  });
+
+  it('applies instance request interceptors', async () => {
+    const { transport, getCalls } = createTransportCapture();
+    const client = axios.create({
+      baseURL: 'http://example.com',
+    });
+
+    client.interceptors.request.use((config) => {
+      config.headers = config.headers || {};
+      config.headers['X-From-Interceptor'] = 'yes';
+      return config;
+    });
+
+    await client.get('/intercepted', { transport, proxy: false });
+
+    expect(getCalls()).toHaveLength(1);
+    expect(getCalls()[0].headers['X-From-Interceptor']).toBe('yes');
+  });
+
+  it('applies instance response interceptors', async () => {
+    const { transport } = createTransportCapture('{"name":"axios"}');
+    const client = axios.create({
+      baseURL: 'http://example.com',
+    });
+
+    client.interceptors.response.use((response) => {
+      response.data = Object.assign({}, response.data, {
+        intercepted: true,
+      });
+      return response;
+    });
+
+    const response = await client.get('/response-interceptor', {
+      transport,
+      proxy: false,
+    });
+
+    expect(response.data).toEqual({
+      name: 'axios',
+      intercepted: true,
+    });
+  });
+
+  it('builds URLs with getUri from instance defaults and request params', () => {
+    const client = axios.create({
+      baseURL: 'http://example.com/api',
+      params: {
+        apiKey: 'abc',
+      },
+    });
+
+    const uri = client.getUri({
+      url: '/users',
+      params: {
+        page: 2,
+      },
+    });
+
+    expect(uri).toBe('http://example.com/api/users?apiKey=abc&page=2');
+  });
+});

tests/smoke/esm/tests/interceptors.smoke.test.js

@@ -0,0 +1,149 @@
+import { describe, expect, it } from 'vitest';
+
+import { EventEmitter } from 'events';
+import { PassThrough } from 'stream';
+import axios from 'axios';
+
+const createTransport = (responseBody) => {
+  const calls = [];
+
+  const transport = {
+    request(options, onResponse) {
+      calls.push(options);
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+      req.end = () => {
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end(responseBody ? responseBody : '{"value":"ok"}');
+      };
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCalls: () => calls,
+  };
+};
+
+describe('interceptors compat (dist export only)', () => {
+  it('applies request interceptors before dispatch', async () => {
+    const { transport, getCalls } = createTransport();
+    const client = axios.create();
+
+    client.interceptors.request.use((config) => {
+      config.headers = config.headers || {};
+      config.headers['X-One'] = '1';
+      return config;
+    });
+
+    client.interceptors.request.use((config) => {
+      config.headers['X-Two'] = '2';
+      return config;
+    });
+
+    await client.get('http://example.com/resource', {
+      transport,
+      proxy: false,
+    });
+
+    expect(getCalls()).toHaveLength(1);
+    expect(getCalls()[0].headers['X-One']).toBe('1');
+    expect(getCalls()[0].headers['X-Two']).toBe('2');
+  });
+
+  it('applies response interceptors in registration order', async () => {
+    const { transport } = createTransport('{"n":1}');
+    const client = axios.create();
+
+    client.interceptors.response.use((response) => {
+      response.data.n += 1;
+      return response;
+    });
+
+    client.interceptors.response.use((response) => {
+      response.data.n *= 10;
+      return response;
+    });
+
+    const response = await client.get('http://example.com/resource', {
+      transport,
+      proxy: false,
+    });
+
+    expect(response.data.n).toBe(20);
+  });
+
+  it('supports ejecting request interceptors', async () => {
+    const { transport, getCalls } = createTransport();
+    const client = axios.create();
+
+    const id = client.interceptors.request.use((config) => {
+      config.headers = config.headers || {};
+      config.headers['X-Ejected'] = 'yes';
+      return config;
+    });
+
+    client.interceptors.request.eject(id);
+
+    await client.get('http://example.com/resource', {
+      transport,
+      proxy: false,
+    });
+
+    expect(getCalls()).toHaveLength(1);
+    expect(getCalls()[0].headers['X-Ejected']).toBeUndefined();
+  });
+
+  it('supports async request interceptors', async () => {
+    const { transport, getCalls } = createTransport();
+    const client = axios.create();
+
+    client.interceptors.request.use(async (config) => {
+      await Promise.resolve();
+      config.headers = config.headers || {};
+      config.headers['X-Async'] = 'true';
+      return config;
+    });
+
+    await client.get('http://example.com/resource', {
+      transport,
+      proxy: false,
+    });
+
+    expect(getCalls()[0].headers['X-Async']).toBe('true');
+  });
+
+  it('propagates errors thrown by request interceptors', async () => {
+    const { transport, getCalls } = createTransport();
+    const client = axios.create();
+
+    client.interceptors.request.use(() => {
+      throw new Error('blocked-by-interceptor');
+    });
+
+    const err = await client
+      .get('http://example.com/resource', {
+        transport,
+        proxy: false,
+      })
+      .catch((e) => e);
+
+    expect(err).toBeInstanceOf(Error);
+    expect(err.message).toContain('blocked-by-interceptor');
+    expect(getCalls()).toHaveLength(0);
+  });
+});

tests/smoke/esm/tests/progress.smoke.test.js

@@ -0,0 +1,113 @@
+import { describe, expect, it } from 'vitest';
+
+import { Readable, Writable, PassThrough } from 'stream';
+import axios from 'axios';
+
+const createProgressTransport = (config) => {
+  const opts = config || {};
+  const responseChunks = opts.responseChunks || ['ok'];
+  const responseHeaders = opts.responseHeaders || {};
+
+  return {
+    request(_options, onResponse) {
+      const req = new Writable({
+        write(_chunk, _encoding, callback) {
+          callback();
+        },
+      });
+
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.close = () => {
+        req.destroyed = true;
+      };
+
+      const originalDestroy = req.destroy.bind(req);
+      req.destroy = (...args) => {
+        req.destroyed = true;
+        return originalDestroy(...args);
+      };
+
+      const originalEnd = req.end.bind(req);
+      req.end = (...args) => {
+        originalEnd(...args);
+
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = Object.assign(
+          {
+            'content-type': 'text/plain',
+          },
+          responseHeaders
+        );
+        res.req = req;
+
+        onResponse(res);
+
+        responseChunks.forEach((chunk) => {
+          res.write(chunk);
+        });
+        res.end();
+      };
+
+      return req;
+    },
+  };
+};
+
+describe('progress compat (dist export only)', () => {
+  it('emits upload progress events for stream payloads', async () => {
+    const samples = [];
+    const payload = ['abc', 'def', 'ghi'];
+    const total = payload.join('').length;
+
+    await axios.post('http://example.com/upload', Readable.from(payload), {
+      proxy: false,
+      headers: {
+        'Content-Length': String(total),
+      },
+      onUploadProgress: ({ loaded, total: reportedTotal, upload }) => {
+        samples.push({ loaded, total: reportedTotal, upload });
+      },
+      transport: createProgressTransport({
+        responseChunks: ['uploaded'],
+      }),
+    });
+
+    expect(samples.length).toBeGreaterThan(0);
+    expect(samples[samples.length - 1]).toMatchObject({
+      loaded: total,
+      total,
+      upload: true,
+    });
+  });
+
+  it('emits download progress events', async () => {
+    const samples = [];
+    const chunks = ['ab', 'cd', 'ef'];
+    const total = chunks.join('').length;
+
+    const response = await axios.get('http://example.com/download', {
+      proxy: false,
+      responseType: 'text',
+      onDownloadProgress: ({ loaded, total: reportedTotal, download }) => {
+        samples.push({ loaded, total: reportedTotal, download });
+      },
+      transport: createProgressTransport({
+        responseChunks: chunks,
+        responseHeaders: {
+          'content-length': String(total),
+        },
+      }),
+    });
+
+    expect(response.data).toBe('abcdef');
+    expect(samples.length).toBeGreaterThan(0);
+    expect(samples[samples.length - 1]).toMatchObject({
+      loaded: total,
+      total,
+      download: true,
+    });
+  });
+});

tests/smoke/esm/tests/rateLimit.smoke.test.js

@@ -0,0 +1,105 @@
+import { describe, expect, it } from 'vitest';
+
+import { EventEmitter } from 'events';
+import { PassThrough } from 'stream';
+import axios from 'axios';
+
+const createTransportCapture = () => {
+  let capturedOptions;
+
+  const transport = {
+    request(options, onResponse) {
+      capturedOptions = options;
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.write = () => true;
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+      req.end = () => {
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end('{"ok":true}');
+      };
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCapturedOptions: () => capturedOptions,
+  };
+};
+
+describe('rateLimit compat (dist export only)', () => {
+  it('accepts numeric maxRate config', async () => {
+    const response = await axios.get('http://example.com/rate', {
+      maxRate: 1024,
+      adapter: async (config) => ({
+        data: { maxRate: config.maxRate },
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data.maxRate).toBe(1024);
+  });
+
+  it('accepts tuple maxRate config [upload, download]', async () => {
+    const response = await axios.get('http://example.com/rate', {
+      maxRate: [2048, 4096],
+      adapter: async (config) => ({
+        data: { maxRate: config.maxRate },
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data.maxRate).toEqual([2048, 4096]);
+  });
+
+  it('merges instance and request maxRate values', async () => {
+    const client = axios.create({
+      maxRate: [1000, 2000],
+    });
+
+    const response = await client.get('http://example.com/rate', {
+      maxRate: [3000, 4000],
+      adapter: async (config) => ({
+        data: { maxRate: config.maxRate },
+        status: 200,
+        statusText: 'OK',
+        headers: {},
+        config,
+      }),
+    });
+
+    expect(response.data.maxRate).toEqual([3000, 4000]);
+  });
+
+  it('supports maxRate in node transport flow without errors', async () => {
+    const { transport, getCapturedOptions } = createTransportCapture();
+
+    const response = await axios.get('http://example.com/rate', {
+      proxy: false,
+      maxRate: [1500, 2500],
+      transport,
+    });
+
+    expect(response.status).toBe(200);
+    expect(getCapturedOptions().method).toBe('GET');
+    expect(getCapturedOptions().path).toBe('/rate');
+  });
+});

tests/smoke/esm/tests/timeout.smoke.test.js

@@ -0,0 +1,116 @@
+import { describe, expect, it } from 'vitest';
+
+import { EventEmitter } from 'events';
+import { PassThrough } from 'stream';
+import axios from 'axios';
+
+const createTransport = (config) => {
+  const opts = config || {};
+
+  return {
+    request(_options, onResponse) {
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req._timeoutCallback = null;
+
+      req.setTimeout = (_ms, callback) => {
+        req._timeoutCallback = callback;
+      };
+
+      req.write = () => true;
+
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+
+      req.end = () => {
+        if (opts.triggerTimeout && req._timeoutCallback) {
+          req._timeoutCallback();
+          return;
+        }
+
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+
+        onResponse(res);
+        res.end(opts.body === undefined ? '{"ok":true}' : opts.body);
+      };
+
+      return req;
+    },
+  };
+};
+
+describe('timeout compat (dist export only)', () => {
+  it('rejects with ECONNABORTED on timeout', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: 25,
+        transport: createTransport({ triggerTimeout: true }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).toBe(true);
+    expect(err.code).toBe('ECONNABORTED');
+    expect(err.message).toBe('timeout of 25ms exceeded');
+  });
+
+  it('uses timeoutErrorMessage when provided', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: 25,
+        timeoutErrorMessage: 'custom timeout',
+        transport: createTransport({ triggerTimeout: true }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).toBe(true);
+    expect(err.code).toBe('ECONNABORTED');
+    expect(err.message).toBe('custom timeout');
+  });
+
+  it('accepts timeout as a numeric string', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: '30',
+        transport: createTransport({ triggerTimeout: true }),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).toBe(true);
+    expect(err.code).toBe('ECONNABORTED');
+    expect(err.message).toBe('timeout of 30ms exceeded');
+  });
+
+  it('rejects with ERR_BAD_OPTION_VALUE when timeout is not parsable', async () => {
+    const err = await axios
+      .get('http://example.com/timeout', {
+        proxy: false,
+        timeout: { invalid: true },
+        transport: createTransport(),
+      })
+      .catch((e) => e);
+
+    expect(axios.isAxiosError(err)).toBe(true);
+    expect(err.code).toBe('ERR_BAD_OPTION_VALUE');
+    expect(err.message).toBe('error trying to parse `config.timeout` to int');
+  });
+
+  it('does not time out when timeout is 0', async () => {
+    const response = await axios.get('http://example.com/no-timeout', {
+      proxy: false,
+      timeout: 0,
+      transport: createTransport({ body: '{"ok":true}' }),
+    });
+
+    expect(response.status).toBe(200);
+    expect(response.data).toEqual({ ok: true });
+  });
+});

tests/smoke/esm/tests/urlencode.smoke.test.js

@@ -0,0 +1,146 @@
+import { describe, expect, it } from 'vitest';
+
+import { EventEmitter } from 'events';
+import { PassThrough } from 'stream';
+import axios from 'axios';
+
+const createEchoTransport = () => {
+  let capturedOptions;
+
+  const transport = {
+    request(options, onResponse) {
+      capturedOptions = options;
+      const chunks = [];
+
+      const req = new EventEmitter();
+      req.destroyed = false;
+      req.setTimeout = () => {};
+      req.destroy = () => {
+        req.destroyed = true;
+      };
+      req.close = req.destroy;
+      req.write = (chunk) => {
+        chunks.push(Buffer.from(chunk));
+        return true;
+      };
+      req.end = (chunk) => {
+        if (chunk) {
+          chunks.push(Buffer.from(chunk));
+        }
+
+        const res = new PassThrough();
+        res.statusCode = 200;
+        res.statusMessage = 'OK';
+        res.headers = { 'content-type': 'application/json' };
+        res.req = req;
+        onResponse(res);
+        res.end(
+          JSON.stringify({
+            path: options.path,
+            body: Buffer.concat(chunks).toString('utf8'),
+            contentType:
+              options.headers &&
+              (options.headers['Content-Type'] || options.headers['content-type']),
+          })
+        );
+      };
+
+      return req;
+    },
+  };
+
+  return {
+    transport,
+    getCapturedOptions: () => capturedOptions,
+  };
+};
+
+describe('urlencode compat (dist export only)', () => {
+  it('serializes params into request URL', async () => {
+    const { transport } = createEchoTransport();
+
+    const response = await axios.get('http://example.com/search', {
+      proxy: false,
+      transport,
+      params: {
+        q: 'axios docs',
+        page: 2,
+      },
+    });
+
+    expect(response.data.path).toBe('/search?q=axios+docs&page=2');
+  });
+
+  it('supports custom paramsSerializer function', async () => {
+    const { transport } = createEchoTransport();
+
+    const response = await axios.get('http://example.com/search', {
+      proxy: false,
+      transport,
+      params: { q: 'ignored' },
+      paramsSerializer: () => 'fixed=1',
+    });
+
+    expect(response.data.path).toBe('/search?fixed=1');
+  });
+
+  it('supports URLSearchParams payloads', async () => {
+    const { transport } = createEchoTransport();
+    const payload = new URLSearchParams();
+    payload.append('name', 'axios');
+    payload.append('mode', 'compat');
+
+    const response = await axios.post('http://example.com/form', payload, {
+      proxy: false,
+      transport,
+    });
+
+    expect(response.data.body).toBe('name=axios&mode=compat');
+    expect(response.data.contentType).toContain('application/x-www-form-urlencoded');
+  });
+
+  it('serializes object payload when content-type is application/x-www-form-urlencoded', async () => {
+    const { transport } = createEchoTransport();
+
+    const response = await axios.post(
+      'http://example.com/form',
+      {
+        name: 'axios',
+        mode: 'compat',
+      },
+      {
+        proxy: false,
+        transport,
+        headers: {
+          'content-type': 'application/x-www-form-urlencoded',
+        },
+      }
+    );
+
+    expect(response.data.body).toBe('name=axios&mode=compat');
+    expect(response.data.contentType).toContain('application/x-www-form-urlencoded');
+  });
+
+  it('respects formSerializer options for index formatting', async () => {
+    const { transport } = createEchoTransport();
+
+    const response = await axios.post(
+      'http://example.com/form',
+      {
+        arr: ['1', '2'],
+      },
+      {
+        proxy: false,
+        transport,
+        headers: {
+          'content-type': 'application/x-www-form-urlencoded',
+        },
+        formSerializer: {
+          indexes: true,
+        },
+      }
+    );
+
+    expect(response.data.body).toBe('arr%5B0%5D=1&arr%5B1%5D=2');
+  });
+});

tests/smoke/esm/vitest.config.js

@@ -0,0 +1,17 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    testTimeout: 10000,
+    projects: [
+      {
+        test: {
+          name: 'smoke',
+          environment: 'node',
+          include: ['tests/**/*.smoke.test.js'],
+          setupFiles: [],
+        },
+      },
+    ],
+  },
+});

tests/unit/adapters/fetch.test.js

@@ -1,9 +1,8 @@
-import { afterEach, describe, it, vi } from 'vitest';
+import { describe, it, vi } from 'vitest';
 import assert from 'assert';
 import {
   startHTTPServer,
   stopHTTPServer,
-  LOCAL_SERVER_URL,
   setTimeoutAsync,
   makeReadableStream,
   generateReadable,
@@ -15,6 +14,9 @@ import { AbortController } from 'abortcontroller-polyfill/dist/cjs-ponyfill.js';
 import util from 'util';
 import NodeFormData from 'form-data';
 
+const SERVER_PORT = 8010;
+const LOCAL_SERVER_URL = `http://localhost:${SERVER_PORT}`;
+
 const pipelineAsync = util.promisify(stream.pipeline);
 
 const fetchAxios = axios.create({
@@ -22,69 +24,85 @@ const fetchAxios = axios.create({
   adapter: 'fetch',
 });
 
-let server;
-
 describe.runIf(typeof fetch === 'function')('supports fetch with nodejs', () => {
-  afterEach(async () => {
-    await stopHTTPServer(server);
-
-    server = null;
-  });
-
   describe('responses', () => {
     it('should support text response type', async () => {
       const originalData = 'my data';
 
-      server = await startHTTPServer((req, res) => res.end(originalData));
-
-      const { data } = await fetchAxios.get('/', {
-        responseType: 'text',
+      const server = await startHTTPServer((req, res) => res.end(originalData), {
+        port: SERVER_PORT,
       });
 
-      assert.deepStrictEqual(data, originalData);
+      try {
+        const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
+          responseType: 'text',
+        });
+
+        assert.deepStrictEqual(data, originalData);
+      } finally {
+        await stopHTTPServer(server);
+      }
     });
 
     it('should support arraybuffer response type', async () => {
       const originalData = 'my data';
 
-      server = await startHTTPServer((req, res) => res.end(originalData));
-
-      const { data } = await fetchAxios.get('/', {
-        responseType: 'arraybuffer',
+      const server = await startHTTPServer((req, res) => res.end(originalData), {
+        port: SERVER_PORT,
       });
 
-      assert.deepStrictEqual(
-        data,
-        Uint8Array.from(await new TextEncoder().encode(originalData)).buffer
-      );
+      try {
+        const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
+          responseType: 'arraybuffer',
+        });
+
+        assert.deepStrictEqual(
+          data,
+          Uint8Array.from(await new TextEncoder().encode(originalData)).buffer
+        );
+      } finally {
+        await stopHTTPServer(server);
+      }
     });
 
     it('should support blob response type', async () => {
       const originalData = 'my data';
 
-      server = await startHTTPServer((req, res) => res.end(originalData));
-
-      const { data } = await fetchAxios.get('/', {
-        responseType: 'blob',
+      const server = await startHTTPServer((req, res) => res.end(originalData), {
+        port: SERVER_PORT,
       });
 
-      assert.deepStrictEqual(data, new Blob([originalData]));
+      try {
+        const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
+          responseType: 'blob',
+        });
+
+        assert.deepStrictEqual(data, new Blob([originalData]));
+      } finally {
+        await stopHTTPServer(server);
+      }
     });
 
     it('should support stream response type', async () => {
       const originalData = 'my data';
 
-      server = await startHTTPServer((req, res) => res.end(originalData));
-
-      const { data } = await fetchAxios.get('/', {
-        responseType: 'stream',
+      const server = await startHTTPServer((req, res) => res.end(originalData), {
+        port: SERVER_PORT,
       });
 
-      assert.ok(data instanceof ReadableStream, 'data is not instanceof ReadableStream');
+      try {
+        const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
+          responseType: 'stream',
+        });
 
-      const response = new Response(data);
+        assert.ok(data instanceof ReadableStream, 'data is not instanceof ReadableStream');
 
-      assert.deepStrictEqual(await response.text(), originalData);
+        const response = new Response(data);
+
+        assert.deepStrictEqual(await response.text(), originalData);
+      } finally {
+        await stopHTTPServer(server);
+      }
     });
 
     it('should support formData response type', async () => {
@@ -92,295 +110,382 @@ describe.runIf(typeof fetch === 'function')('supports fetch with nodejs', () =>
 
       originalData.append('x', '123');
 
-      server = await startHTTPServer(async (req, res) => {
-        const response = await new Response(originalData);
+      const server = await startHTTPServer(
+        async (req, res) => {
+          const response = await new Response(originalData);
 
-        res.setHeader('Content-Type', response.headers.get('Content-Type'));
+          res.setHeader('Content-Type', response.headers.get('Content-Type'));
 
-        res.end(await response.text());
-      });
-
-      const { data } = await fetchAxios.get('/', {
-        responseType: 'formdata',
-      });
-
-      assert.ok(data instanceof FormData, 'data is not instanceof FormData');
-
-      assert.deepStrictEqual(
-        Object.fromEntries(data.entries()),
-        Object.fromEntries(originalData.entries())
+          res.end(await response.text());
+        },
+        { port: SERVER_PORT }
       );
+
+      try {
+        const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
+          responseType: 'formdata',
+        });
+
+        assert.ok(data instanceof FormData, 'data is not instanceof FormData');
+
+        assert.deepStrictEqual(
+          Object.fromEntries(data.entries()),
+          Object.fromEntries(originalData.entries())
+        );
+      } finally {
+        await stopHTTPServer(server);
+      }
     }, 5000);
 
     it('should support json response type', async () => {
       const originalData = { x: 'my data' };
 
-      server = await startHTTPServer((req, res) => res.end(JSON.stringify(originalData)));
-
-      const { data } = await fetchAxios.get('/', {
-        responseType: 'json',
+      const server = await startHTTPServer((req, res) => res.end(JSON.stringify(originalData)), {
+        port: SERVER_PORT,
       });
 
-      assert.deepStrictEqual(data, originalData);
+      try {
+        const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
+          responseType: 'json',
+        });
+
+        assert.deepStrictEqual(data, originalData);
+      } finally {
+        await stopHTTPServer(server);
+      }
     });
   });
 
   describe('progress', () => {
     describe('upload', () => {
       it('should support upload progress capturing', async () => {
-        server = await startHTTPServer({
-          rate: 100 * 1024,
-        });
-
-        let content = '';
-        const count = 10;
-        const chunk = 'test';
-        const chunkLength = Buffer.byteLength(chunk);
-        const contentLength = count * chunkLength;
-
-        const readable = stream.Readable.from(
-          (async function* () {
-            let i = count;
-
-            while (i-- > 0) {
-              await setTimeoutAsync(1100);
-              content += chunk;
-              yield chunk;
-            }
-          })()
+        const server = await startHTTPServer(
+          {
+            rate: 100 * 1024,
+          },
+          { port: SERVER_PORT }
         );
 
-        const samples = [];
+        try {
+          let content = '';
+          const count = 10;
+          const chunk = 'test';
+          const chunkLength = Buffer.byteLength(chunk);
+          const contentLength = count * chunkLength;
 
-        const { data } = await fetchAxios.post('/', readable, {
-          onUploadProgress: ({ loaded, total, progress, bytes, upload }) => {
-            console.log(
-              `Upload Progress ${loaded} from ${total} bytes (${(progress * 100).toFixed(1)}%)`
-            );
+          const readable = stream.Readable.from(
+            (async function* () {
+              let i = count;
 
-            samples.push({
-              loaded,
-              total,
-              progress,
-              bytes,
-              upload,
-            });
-          },
-          headers: {
-            'Content-Length': contentLength,
-          },
-          responseType: 'text',
-        });
-
-        await setTimeoutAsync(500);
-
-        assert.strictEqual(data, content);
-
-        assert.deepStrictEqual(
-          samples,
-          Array.from(
-            (function* () {
-              for (let i = 1; i <= 10; i++) {
-                yield {
-                  loaded: chunkLength * i,
-                  total: contentLength,
-                  progress: (chunkLength * i) / contentLength,
-                  bytes: 4,
-                  upload: true,
-                };
+              while (i-- > 0) {
+                await setTimeoutAsync(1100);
+                content += chunk;
+                yield chunk;
               }
             })()
-          )
-        );
+          );
+
+          const samples = [];
+
+          const { data } = await fetchAxios.post(
+            `http://localhost:${server.address().port}/`,
+            readable,
+            {
+              onUploadProgress: ({ loaded, total, progress, bytes, upload }) => {
+                console.log(
+                  `Upload Progress ${loaded} from ${total} bytes (${(progress * 100).toFixed(1)}%)`
+                );
+
+                samples.push({
+                  loaded,
+                  total,
+                  progress,
+                  bytes,
+                  upload,
+                });
+              },
+              headers: {
+                'Content-Length': contentLength,
+              },
+              responseType: 'text',
+            }
+          );
+
+          await setTimeoutAsync(500);
+
+          assert.strictEqual(data, content);
+
+          assert.deepStrictEqual(
+            samples,
+            Array.from(
+              (function* () {
+                for (let i = 1; i <= 10; i++) {
+                  yield {
+                    loaded: chunkLength * i,
+                    total: contentLength,
+                    progress: (chunkLength * i) / contentLength,
+                    bytes: 4,
+                    upload: true,
+                  };
+                }
+              })()
+            )
+          );
+        } finally {
+          await stopHTTPServer(server);
+        }
       }, 15000);
 
       it('should not fail with get method', async () => {
-        server = await startHTTPServer((req, res) => res.end('OK'));
+        const server = await startHTTPServer((req, res) => res.end('OK'), { port: SERVER_PORT });
 
-        const { data } = await fetchAxios.get('/', {
-          onUploadProgress() {},
-        });
+        try {
+          const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
+            onUploadProgress() {},
+          });
 
-        assert.strictEqual(data, 'OK');
+          assert.strictEqual(data, 'OK');
+        } finally {
+          await stopHTTPServer(server);
+        }
       });
     });
 
     describe('download', () => {
       it('should support download progress capturing', async () => {
-        server = await startHTTPServer({
-          rate: 100 * 1024,
-        });
-
-        let content = '';
-        const count = 10;
-        const chunk = 'test';
-        const chunkLength = Buffer.byteLength(chunk);
-        const contentLength = count * chunkLength;
-
-        const readable = stream.Readable.from(
-          (async function* () {
-            let i = count;
-
-            while (i-- > 0) {
-              await setTimeoutAsync(1100);
-              content += chunk;
-              yield chunk;
-            }
-          })()
+        const server = await startHTTPServer(
+          {
+            rate: 100 * 1024,
+          },
+          {
+            port: SERVER_PORT,
+          }
         );
 
-        const samples = [];
+        try {
+          let content = '';
+          const count = 10;
+          const chunk = 'test';
+          const chunkLength = Buffer.byteLength(chunk);
+          const contentLength = count * chunkLength;
 
-        const { data } = await fetchAxios.post('/', readable, {
-          onDownloadProgress: ({ loaded, total, progress, bytes, download }) => {
-            console.log(
-              `Download Progress ${loaded} from ${total} bytes (${(progress * 100).toFixed(1)}%)`
-            );
+          const readable = stream.Readable.from(
+            (async function* () {
+              let i = count;
 
-            samples.push({
-              loaded,
-              total,
-              progress,
-              bytes,
-              download,
-            });
-          },
-          headers: {
-            'Content-Length': contentLength,
-          },
-          responseType: 'text',
-          maxRedirects: 0,
-        });
-
-        await setTimeoutAsync(500);
-
-        assert.strictEqual(data, content);
-
-        assert.deepStrictEqual(
-          samples,
-          Array.from(
-            (function* () {
-              for (let i = 1; i <= 10; i++) {
-                yield {
-                  loaded: chunkLength * i,
-                  total: contentLength,
-                  progress: (chunkLength * i) / contentLength,
-                  bytes: 4,
-                  download: true,
-                };
+              while (i-- > 0) {
+                await setTimeoutAsync(1100);
+                content += chunk;
+                yield chunk;
               }
             })()
-          )
-        );
+          );
+
+          const samples = [];
+
+          const { data } = await fetchAxios.post(
+            `http://localhost:${server.address().port}/`,
+            readable,
+            {
+              onDownloadProgress: ({ loaded, total, progress, bytes, download }) => {
+                console.log(
+                  `Download Progress ${loaded} from ${total} bytes (${(progress * 100).toFixed(1)}%)`
+                );
+
+                samples.push({
+                  loaded,
+                  total,
+                  progress,
+                  bytes,
+                  download,
+                });
+              },
+              headers: {
+                'Content-Length': contentLength,
+              },
+              responseType: 'text',
+              maxRedirects: 0,
+            }
+          );
+
+          await setTimeoutAsync(500);
+
+          assert.strictEqual(data, content);
+
+          assert.deepStrictEqual(
+            samples,
+            Array.from(
+              (function* () {
+                for (let i = 1; i <= 10; i++) {
+                  yield {
+                    loaded: chunkLength * i,
+                    total: contentLength,
+                    progress: (chunkLength * i) / contentLength,
+                    bytes: 4,
+                    download: true,
+                  };
+                }
+              })()
+            )
+          );
+        } finally {
+          await stopHTTPServer(server);
+        }
       }, 15000);
     });
   });
 
   it('should support basic auth', async () => {
-    server = await startHTTPServer((req, res) => res.end(req.headers.authorization));
+    const server = await startHTTPServer((req, res) => res.end(req.headers.authorization), {
+      port: SERVER_PORT,
+    });
 
-    const user = 'foo';
-    const headers = { Authorization: 'Bearer 1234' };
-    const res = await axios.get(`http://${user}@localhost:4444/`, { headers });
+    try {
+      const user = 'foo';
+      const headers = { Authorization: 'Bearer 1234' };
+      const res = await axios.get(`http://${user}@localhost:${server.address().port}/`, {
+        headers,
+      });
 
-    const base64 = Buffer.from(`${user}:`, 'utf8').toString('base64');
-    assert.equal(res.data, `Basic ${base64}`);
+      const base64 = Buffer.from(`${user}:`, 'utf8').toString('base64');
+      assert.equal(res.data, `Basic ${base64}`);
+    } finally {
+      await stopHTTPServer(server);
+    }
   });
 
   it('should support stream.Readable as a payload', async () => {
-    server = await startHTTPServer();
+    const server = await startHTTPServer(async (req, res) => res.end('OK'), { port: SERVER_PORT });
 
-    const { data } = await fetchAxios.post('/', stream.Readable.from('OK'));
+    try {
+      const { data } = await fetchAxios.post(
+        `http://localhost:${server.address().port}/`,
+        stream.Readable.from('OK')
+      );
 
-    assert.strictEqual(data, 'OK');
+      assert.strictEqual(data, 'OK');
+    } finally {
+      await stopHTTPServer(server);
+    }
   });
 
   describe('request aborting', () => {
     it('should be able to abort the request stream', async () => {
-      server = await startHTTPServer({
-        rate: 100000,
-        useBuffering: true,
-      });
+      const server = await startHTTPServer(
+        {
+          rate: 100000,
+          useBuffering: true,
+        },
+        { port: SERVER_PORT }
+      );
 
-      const controller = new AbortController();
+      try {
+        const controller = new AbortController();
 
-      setTimeout(() => {
-        controller.abort();
-      }, 500);
+        setTimeout(() => {
+          controller.abort();
+        }, 500);
 
-      await assert.rejects(async () => {
-        await fetchAxios.post('/', makeReadableStream(), {
-          responseType: 'stream',
-          signal: controller.signal,
-        });
-      }, /CanceledError/);
+        await assert.rejects(async () => {
+          await fetchAxios.post(
+            `http://localhost:${server.address().port}/`,
+            makeReadableStream(),
+            {
+              responseType: 'stream',
+              signal: controller.signal,
+            }
+          );
+        }, /CanceledError/);
+      } finally {
+        await stopHTTPServer(server);
+      }
     });
 
     it('should be able to abort the response stream', async () => {
-      server = await startHTTPServer((req, res) => {
-        pipelineAsync(generateReadable(10000, 10), res).catch(() => {
-          // Client-side abort intentionally closes the stream early in this test.
+      const server = await startHTTPServer(
+        (req, res) => {
+          pipelineAsync(generateReadable(10000, 10), res).catch(() => {
+            // Client-side abort intentionally closes the stream early in this test.
+          });
+        },
+        { port: SERVER_PORT }
+      );
+
+      try {
+        const controller = new AbortController();
+
+        setTimeout(() => {
+          controller.abort(new Error('test'));
+        }, 800);
+
+        const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
+          responseType: 'stream',
+          signal: controller.signal,
         });
-      });
 
-      const controller = new AbortController();
-
-      setTimeout(() => {
-        controller.abort(new Error('test'));
-      }, 800);
-
-      const { data } = await fetchAxios.get('/', {
-        responseType: 'stream',
-        signal: controller.signal,
-      });
-
-      await assert.rejects(async () => {
-        await data.pipeTo(makeEchoStream());
-      }, /^(AbortError|CanceledError):/);
+        await assert.rejects(async () => {
+          await data.pipeTo(makeEchoStream());
+        }, /^(AbortError|CanceledError):/);
+      } finally {
+        await stopHTTPServer(server);
+      }
     });
   });
 
   it('should support a timeout', async () => {
-    server = await startHTTPServer(async (req, res) => {
-      await setTimeoutAsync(1000);
-      res.end('OK');
-    });
+    const server = await startHTTPServer(
+      async (req, res) => {
+        await setTimeoutAsync(1000);
+        res.end('OK');
+      },
+      { port: SERVER_PORT }
+    );
 
-    const timeout = 500;
+    try {
+      const timeout = 500;
 
-    const ts = Date.now();
+      const ts = Date.now();
 
-    await assert.rejects(async () => {
-      await fetchAxios('/', {
-        timeout,
-      });
-    }, /timeout/);
+      await assert.rejects(async () => {
+        await fetchAxios(`http://localhost:${server.address().port}/`, {
+          timeout,
+        });
+      }, /timeout/);
 
-    const passed = Date.now() - ts;
+      const passed = Date.now() - ts;
 
-    assert.ok(passed >= timeout - 5, `early cancellation detected (${passed} ms)`);
+      assert.ok(passed >= timeout - 5, `early cancellation detected (${passed} ms)`);
+    } finally {
+      await stopHTTPServer(server);
+    }
   });
 
   it('should combine baseURL and url', async () => {
-    server = await startHTTPServer();
+    const server = await startHTTPServer(async (req, res) => res.end('OK'), { port: SERVER_PORT });
+    try {
+      const res = await fetchAxios('/foo');
 
-    const res = await fetchAxios('/foo');
-
-    assert.equal(res.config.baseURL, LOCAL_SERVER_URL);
-    assert.equal(res.config.url, '/foo');
+      assert.equal(res.config.baseURL, LOCAL_SERVER_URL);
+      assert.equal(res.config.url, '/foo');
+    } finally {
+      await stopHTTPServer(server);
+    }
   });
 
   it('should support params', async () => {
-    server = await startHTTPServer((req, res) => res.end(req.url));
+    const server = await startHTTPServer((req, res) => res.end(req.url), { port: SERVER_PORT });
+    try {
+      const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/?test=1`, {
+        params: {
+          foo: 1,
+          bar: 2,
+        },
+      });
 
-    const { data } = await fetchAxios.get('/?test=1', {
-      params: {
-        foo: 1,
-        bar: 2,
-      },
-    });
-
-    assert.strictEqual(data, '/?test=1&foo=1&bar=2');
+      assert.strictEqual(data, '/?test=1&foo=1&bar=2');
+    } finally {
+      await stopHTTPServer(server);
+    }
   });
 
   it('should handle fetch failed error as an AxiosError with ERR_NETWORK code', async () => {
@@ -394,16 +499,23 @@ describe.runIf(typeof fetch === 'function')('supports fetch with nodejs', () =>
   });
 
   it('should get response headers', async () => {
-    server = await startHTTPServer((req, res) => {
-      res.setHeader('foo', 'bar');
-      res.end(req.url);
-    });
+    const server = await startHTTPServer(
+      (req, res) => {
+        res.setHeader('foo', 'bar');
+        res.end(req.url);
+      },
+      { port: SERVER_PORT }
+    );
 
-    const { headers } = await fetchAxios.get('/', {
-      responseType: 'stream',
-    });
+    try {
+      const { headers } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
+        responseType: 'stream',
+      });
 
-    assert.strictEqual(headers.get('foo'), 'bar');
+      assert.strictEqual(headers.get('foo'), 'bar');
+    } finally {
+      await stopHTTPServer(server);
+    }
   });
 
   describe('fetch adapter - Content-Type handling', () => {
@@ -411,13 +523,20 @@ describe.runIf(typeof fetch === 'function')('supports fetch with nodejs', () =>
       const form = new NodeFormData();
       form.append('foo', 'bar');
 
-      server = await startHTTPServer((req, res) => {
-        const contentType = req.headers['content-type'];
-        assert.match(contentType, /^multipart\/form-data; boundary=/i);
-        res.end('OK');
-      });
+      const server = await startHTTPServer(
+        (req, res) => {
+          const contentType = req.headers['content-type'];
+          assert.match(contentType, /^multipart\/form-data; boundary=/i);
+          res.end('OK');
+        },
+        { port: SERVER_PORT }
+      );
 
-      await fetchAxios.post('/form', form);
+      try {
+        await fetchAxios.post(`http://localhost:${server.address().port}/form`, form);
+      } finally {
+        await stopHTTPServer(server);
+      }
     });
   });
 
@@ -490,15 +609,19 @@ describe.runIf(typeof fetch === 'function')('supports fetch with nodejs', () =>
     });
 
     it('should fallback to the global on undefined env value', async () => {
-      server = await startHTTPServer((req, res) => res.end('OK'));
+      const server = await startHTTPServer((req, res) => res.end('OK'), { port: SERVER_PORT });
 
-      const { data } = await fetchAxios.get('/', {
-        env: {
-          fetch: undefined,
-        },
-      });
+      try {
+        const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
+          env: {
+            fetch: undefined,
+          },
+        });
 
-      assert.strictEqual(data, 'OK');
+        assert.strictEqual(data, 'OK');
+      } finally {
+        await stopHTTPServer(server);
+      }
     });
 
     it('should use current global fetch when env fetch is not specified', async () => {
@@ -513,10 +636,10 @@ describe.runIf(typeof fetch === 'function')('supports fetch with nodejs', () =>
         };
       });
 
-      try {
-        server = await startHTTPServer((req, res) => res.end('OK'));
+      const server = await startHTTPServer((req, res) => res.end('OK'), { port: SERVER_PORT });
 
-        const { data } = await fetchAxios.get('/', {
+      try {
+        const { data } = await fetchAxios.get(`http://localhost:${server.address().port}/`, {
           env: {
             fetch: undefined,
           },
@@ -525,6 +648,7 @@ describe.runIf(typeof fetch === 'function')('supports fetch with nodejs', () =>
         assert.strictEqual(data, 'global');
       } finally {
         vi.stubGlobal('fetch', globalFetch);
+        await stopHTTPServer(server);
       }
     });
   });

tests/unit/adapters/http.test.js

@@ -31,6 +31,11 @@ import bodyParser from 'body-parser';
 import { AbortController } from 'abortcontroller-polyfill/dist/cjs-ponyfill.js';
 import { lookup } from 'dns';
 
+const OPEN_WEB_PORT = 80;
+const SERVER_PORT = 8020;
+const PROXY_PORT = 8030;
+const ALTERNATE_SERVER_PORT = 8040;
+
 describe('supports http with nodejs', () => {
   const adaptersTestsDir = path.join(process.cwd(), 'tests/unit/adapters');
   const thisTestFilePath = path.join(adaptersTestsDir, 'http.test.js');
@@ -59,7 +64,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'application/json');
         res.end(JSON.stringify(data));
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -82,7 +87,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'application/json');
         res.end(JSON.stringify(data));
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -102,7 +107,7 @@ describe('supports http with nodejs', () => {
           res.end();
         }, 1000);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -128,7 +133,7 @@ describe('supports http with nodejs', () => {
           res.end();
         }, 1000);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -154,7 +159,7 @@ describe('supports http with nodejs', () => {
           res.end();
         }, 1000);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -180,7 +185,7 @@ describe('supports http with nodejs', () => {
           res.end();
         }, 1000);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -212,7 +217,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'application/json');
         res.end(JSON.stringify(data));
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -237,7 +242,7 @@ describe('supports http with nodejs', () => {
         const jsonBuffer = Buffer.from(JSON.stringify(data));
         res.end(Buffer.concat([bomBuffer, jsonBuffer]));
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -261,7 +266,7 @@ describe('supports http with nodejs', () => {
 
         res.end(expectedResponse);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -283,7 +288,7 @@ describe('supports http with nodejs', () => {
         res.statusCode = 302;
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -311,7 +316,7 @@ describe('supports http with nodejs', () => {
         res.end();
         i++;
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -333,7 +338,7 @@ describe('supports http with nodejs', () => {
         res.statusCode = 302;
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -362,12 +367,12 @@ describe('supports http with nodejs', () => {
       (req, res) => {
         requestCount += 1;
         if (requestCount <= totalRedirectCount) {
-          res.setHeader('Location', 'http://localhost:8080');
+          res.setHeader('Location', `http://localhost:${SERVER_PORT}`);
           res.writeHead(302);
         }
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     const proxy = await startHTTPServer(
@@ -392,13 +397,13 @@ describe('supports http with nodejs', () => {
           res.end();
         });
       },
-      { port: 4000 }
+      { port: PROXY_PORT }
     );
 
     await axios.get(`http://localhost:${server.address().port}/`, {
       proxy: {
         host: 'localhost',
-        port: 4000,
+        port: PROXY_PORT,
       },
       maxRedirects: totalRedirectCount,
       beforeRedirect: (options) => {
@@ -419,7 +424,7 @@ describe('supports http with nodejs', () => {
         res.statusCode = 400;
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -455,7 +460,7 @@ describe('supports http with nodejs', () => {
       (req, res) => {
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -496,7 +501,7 @@ describe('supports http with nodejs', () => {
           res.end();
         }
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -532,7 +537,7 @@ describe('supports http with nodejs', () => {
           res.setHeader('Content-Encoding', 'gzip');
           res.end(zipped);
         },
-        { port: 8080 }
+        { port: SERVER_PORT }
       );
 
       try {
@@ -552,7 +557,7 @@ describe('supports http with nodejs', () => {
           res.setHeader('Content-Encoding', 'gzip');
           res.end('invalid response');
         },
-        { port: 8080 }
+        { port: SERVER_PORT }
       );
 
       try {
@@ -584,7 +589,7 @@ describe('supports http with nodejs', () => {
           res.setHeader('Content-Encoding', 'gzip');
           res.end(zipped);
         },
-        { port: 8080 }
+        { port: SERVER_PORT }
       );
 
       try {
@@ -661,10 +666,13 @@ describe('supports http with nodejs', () => {
 
         describe(`${typeName} decompression`, () => {
           it('should support decompression', async () => {
-            const server = await startHTTPServer(async (req, res) => {
-              res.setHeader('Content-Encoding', type);
-              res.end(await zipped);
-            });
+            const server = await startHTTPServer(
+              async (req, res) => {
+                res.setHeader('Content-Encoding', type);
+                res.end(await zipped);
+              },
+              { port: SERVER_PORT }
+            );
 
             try {
               const { data } = await axios.get(`http://localhost:${server.address().port}`);
@@ -675,11 +683,14 @@ describe('supports http with nodejs', () => {
           });
 
           it(`should not fail if response content-length header is missing (${type})`, async () => {
-            const server = await startHTTPServer(async (req, res) => {
-              res.setHeader('Content-Encoding', type);
-              res.removeHeader('Content-Length');
-              res.end(await zipped);
-            });
+            const server = await startHTTPServer(
+              async (req, res) => {
+                res.setHeader('Content-Encoding', type);
+                res.removeHeader('Content-Length');
+                res.end(await zipped);
+              },
+              { port: SERVER_PORT }
+            );
 
             try {
               const { data } = await axios.get(`http://localhost:${server.address().port}`);
@@ -690,13 +701,16 @@ describe('supports http with nodejs', () => {
           });
 
           it('should not fail with chunked responses (without Content-Length header)', async () => {
-            const server = await startHTTPServer(async (req, res) => {
-              res.setHeader('Content-Encoding', type);
-              res.setHeader('Transfer-Encoding', 'chunked');
-              res.removeHeader('Content-Length');
-              res.write(await zipped);
-              res.end();
-            });
+            const server = await startHTTPServer(
+              async (req, res) => {
+                res.setHeader('Content-Encoding', type);
+                res.setHeader('Transfer-Encoding', 'chunked');
+                res.removeHeader('Content-Length');
+                res.write(await zipped);
+                res.end();
+              },
+              { port: SERVER_PORT }
+            );
 
             try {
               const { data } = await axios.get(`http://localhost:${server.address().port}`);
@@ -707,11 +721,14 @@ describe('supports http with nodejs', () => {
           });
 
           it('should not fail with an empty response without content-length header (Z_BUF_ERROR)', async () => {
-            const server = await startHTTPServer((req, res) => {
-              res.setHeader('Content-Encoding', type);
-              res.removeHeader('Content-Length');
-              res.end();
-            });
+            const server = await startHTTPServer(
+              (req, res) => {
+                res.setHeader('Content-Encoding', type);
+                res.removeHeader('Content-Length');
+                res.end();
+              },
+              { port: SERVER_PORT }
+            );
 
             try {
               const { data } = await axios.get(`http://localhost:${server.address().port}`);
@@ -722,10 +739,13 @@ describe('supports http with nodejs', () => {
           });
 
           it('should not fail with an empty response with content-length header (Z_BUF_ERROR)', async () => {
-            const server = await startHTTPServer((req, res) => {
-              res.setHeader('Content-Encoding', type);
-              res.end();
-            });
+            const server = await startHTTPServer(
+              (req, res) => {
+                res.setHeader('Content-Encoding', type);
+                res.end();
+              },
+              { port: SERVER_PORT }
+            );
 
             try {
               await axios.get(`http://localhost:${server.address().port}`);
@@ -746,7 +766,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'text/html; charset=UTF-8');
         res.end(str);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -762,7 +782,7 @@ describe('supports http with nodejs', () => {
       (req, res) => {
         res.end(req.headers.authorization);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -783,7 +803,7 @@ describe('supports http with nodejs', () => {
       (req, res) => {
         res.end(req.headers.authorization);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -805,7 +825,7 @@ describe('supports http with nodejs', () => {
       (req, res) => {
         res.end(req.headers['user-agent']);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -824,7 +844,7 @@ describe('supports http with nodejs', () => {
       (req, res) => {
         res.end(req.headers['user-agent']);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -842,7 +862,7 @@ describe('supports http with nodejs', () => {
         assert.strictEqual(req.headers['content-length'], '42');
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -859,7 +879,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'text/html; charset=UTF-8');
         res.end(Array(5000).join('#'));
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -891,7 +911,7 @@ describe('supports http with nodejs', () => {
         res.statusCode = 302;
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -916,7 +936,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'text/html; charset=UTF-8');
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -953,7 +973,7 @@ describe('supports http with nodejs', () => {
           res.end('OK');
         });
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -967,7 +987,7 @@ describe('supports http with nodejs', () => {
   });
 
   it('should display error while parsing params', async () => {
-    const server = await startHTTPServer(() => {}, { port: 8080 });
+    const server = await startHTTPServer(() => {}, { port: SERVER_PORT });
 
     try {
       await assert.rejects(
@@ -1044,7 +1064,7 @@ describe('supports http with nodejs', () => {
         (req, res) => {
           req.pipe(res);
         },
-        { port: 8080 }
+        { port: SERVER_PORT }
       );
 
       try {
@@ -1077,7 +1097,7 @@ describe('supports http with nodejs', () => {
     });
 
     it('should pass errors for a failed stream', async () => {
-      const server = await startHTTPServer(() => {}, { port: 8080 });
+      const server = await startHTTPServer(() => {}, { port: SERVER_PORT });
       const notExistPath = path.join(adaptersTestsDir, 'does_not_exist');
 
       try {
@@ -1148,7 +1168,7 @@ describe('supports http with nodejs', () => {
         assert.strictEqual(req.headers['content-length'], buf.length.toString());
         req.pipe(res);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -1182,7 +1202,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'text/html; charset=UTF-8');
         res.end('12345');
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     const proxy = await startHTTPServer(
@@ -1207,7 +1227,7 @@ describe('supports http with nodejs', () => {
           });
         });
       },
-      { port: 0 }
+      { port: PROXY_PORT }
     );
 
     try {
@@ -1251,9 +1271,9 @@ describe('supports http with nodejs', () => {
             res.setHeader('Content-Type', 'text/html; charset=UTF-8');
             res.end('12345');
           },
-          { port: 8080 }
+          { port: SERVER_PORT }
         )
-        .listen(8080, () => resolve(httpsServer));
+        .listen(SERVER_PORT, () => resolve(httpsServer));
 
       httpsServer.on('error', reject);
     });
@@ -1290,9 +1310,9 @@ describe('supports http with nodejs', () => {
               response.end();
             });
           },
-          { port: 8081 }
+          { port: PROXY_PORT }
         )
-        .listen(8081, () => resolve(httpsProxy));
+        .listen(PROXY_PORT, () => resolve(httpsProxy));
 
       httpsProxy.on('error', reject);
     });
@@ -1324,7 +1344,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'text/html; charset=UTF-8');
         res.end('123456789');
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -1355,7 +1375,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'text/html; charset=UTF-8');
         res.end('4567');
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     const proxy = await startHTTPServer(
@@ -1380,7 +1400,7 @@ describe('supports http with nodejs', () => {
           });
         });
       },
-      { port: 8081 }
+      { port: PROXY_PORT }
     );
 
     const proxyUrl = `http://localhost:${proxy.address().port}/`;
@@ -1458,9 +1478,9 @@ describe('supports http with nodejs', () => {
             res.setHeader('Content-Type', 'text/html; charset=UTF-8');
             res.end('12345');
           },
-          { port: 8080 }
+          { port: SERVER_PORT }
         )
-        .listen(8080, () => resolve(httpsServer));
+        .listen(SERVER_PORT, () => resolve(httpsServer));
 
       httpsServer.on('error', reject);
     });
@@ -1497,9 +1517,9 @@ describe('supports http with nodejs', () => {
               response.end();
             });
           },
-          { port: 8081 }
+          { port: PROXY_PORT }
         )
-        .listen(8081, () => resolve(httpsProxy));
+        .listen(PROXY_PORT, () => resolve(httpsProxy));
 
       httpsProxy.on('error', reject);
     });
@@ -1561,7 +1581,7 @@ describe('supports http with nodejs', () => {
         res.statusCode = 302;
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     const proxy = await startHTTPServer(
@@ -1597,7 +1617,7 @@ describe('supports http with nodejs', () => {
           });
         });
       },
-      { port: 8081 }
+      { port: PROXY_PORT }
     );
 
     const proxyUrl = `http://localhost:${proxy.address().port}`;
@@ -1651,7 +1671,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'text/html; charset=UTF-8');
         res.end('4567');
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     const proxy = await startHTTPServer(
@@ -1676,7 +1696,7 @@ describe('supports http with nodejs', () => {
           });
         });
       },
-      { port: 8081 }
+      { port: PROXY_PORT }
     );
 
     const noProxyValue = 'foo.com, localhost,bar.net , , quix.co';
@@ -1730,7 +1750,7 @@ describe('supports http with nodejs', () => {
         res.setHeader('Content-Type', 'text/html; charset=UTF-8');
         res.end('4567');
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     const proxy = await startHTTPServer(
@@ -1755,7 +1775,7 @@ describe('supports http with nodejs', () => {
           });
         });
       },
-      { port: 8081 }
+      { port: PROXY_PORT }
     );
 
     const noProxyValue = 'foo.com, ,bar.net , quix.co';
@@ -1803,7 +1823,7 @@ describe('supports http with nodejs', () => {
       (req, res) => {
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     const proxy = await startHTTPServer(
@@ -1825,7 +1845,7 @@ describe('supports http with nodejs', () => {
           });
         });
       },
-      { port: 8081 }
+      { port: PROXY_PORT }
     );
 
     try {
@@ -1858,7 +1878,7 @@ describe('supports http with nodejs', () => {
       (req, res) => {
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     const proxy = await startHTTPServer(
@@ -1880,7 +1900,7 @@ describe('supports http with nodejs', () => {
           });
         });
       },
-      { port: 8081 }
+      { port: PROXY_PORT }
     );
 
     const proxyUrl = `http://user:pass@localhost:${proxy.address().port}/`;
@@ -1932,7 +1952,7 @@ describe('supports http with nodejs', () => {
       const proxy = {
         protocol: 'http:',
         host: 'hostname.abc.xyz',
-        port: 3300,
+        port: PROXY_PORT,
         auth: {
           username: '',
           password: '',
@@ -1954,23 +1974,48 @@ describe('supports http with nodejs', () => {
     const testCases = [
       {
         description: 'hostname and trailing colon in protocol',
-        proxyConfig: { hostname: '127.0.0.1', protocol: 'http:', port: 80 },
-        expectedOptions: { host: '127.0.0.1', protocol: 'http:', port: 80, path: destination },
+        proxyConfig: { hostname: '127.0.0.1', protocol: 'http:', port: OPEN_WEB_PORT },
+        expectedOptions: {
+          host: '127.0.0.1',
+          protocol: 'http:',
+          port: OPEN_WEB_PORT,
+          path: destination,
+        },
       },
       {
         description: 'hostname and no trailing colon in protocol',
-        proxyConfig: { hostname: '127.0.0.1', protocol: 'http', port: 80 },
-        expectedOptions: { host: '127.0.0.1', protocol: 'http:', port: 80, path: destination },
+        proxyConfig: { hostname: '127.0.0.1', protocol: 'http', port: OPEN_WEB_PORT },
+        expectedOptions: {
+          host: '127.0.0.1',
+          protocol: 'http:',
+          port: OPEN_WEB_PORT,
+          path: destination,
+        },
       },
       {
         description: 'both hostname and host -> hostname takes precedence',
-        proxyConfig: { hostname: '127.0.0.1', host: '0.0.0.0', protocol: 'http', port: 80 },
-        expectedOptions: { host: '127.0.0.1', protocol: 'http:', port: 80, path: destination },
+        proxyConfig: {
+          hostname: '127.0.0.1',
+          host: '0.0.0.0',
+          protocol: 'http',
+          port: OPEN_WEB_PORT,
+        },
+        expectedOptions: {
+          host: '127.0.0.1',
+          protocol: 'http:',
+          port: OPEN_WEB_PORT,
+          path: destination,
+        },
       },
       {
         description: 'only host and https protocol',
-        proxyConfig: { host: '0.0.0.0', protocol: 'https', port: 80 },
-        expectedOptions: { host: '0.0.0.0', protocol: 'https:', port: 80, path: destination },
+        proxyConfig: { host: '0.0.0.0', protocol: 'https', port: OPEN_WEB_PORT },
+        expectedOptions: {
+          host: '0.0.0.0',
+          protocol: 'https:',
+          port: OPEN_WEB_PORT,
+          path: destination,
+        },
       },
     ];
 
@@ -1994,7 +2039,7 @@ describe('supports http with nodejs', () => {
         // Call cancel() when the request has been sent but no response received.
         source.cancel('Operation has been canceled.');
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -2024,7 +2069,7 @@ describe('supports http with nodejs', () => {
       (req, res) => {
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -2046,7 +2091,7 @@ describe('supports http with nodejs', () => {
           res.end();
         }, 1000);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -2072,9 +2117,9 @@ describe('supports http with nodejs', () => {
               res.end();
             }, 1000);
           },
-          { port: 8080 }
+          { port: SERVER_PORT }
         )
-        .listen(8080, () => resolve(httpsServer));
+        .listen(SERVER_PORT, () => resolve(httpsServer));
 
       httpsServer.on('error', reject);
     });
@@ -2120,7 +2165,7 @@ describe('supports http with nodejs', () => {
         assert.equal(req.headers['user-agent'], `axios/${axios.VERSION}`);
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -2137,7 +2182,7 @@ describe('supports http with nodejs', () => {
         assert.equal('User-Agent' in req.headers, false);
         res.end();
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -2165,7 +2210,7 @@ describe('supports http with nodejs', () => {
           res.destroy();
         }, 200);
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -2190,7 +2235,7 @@ describe('supports http with nodejs', () => {
       (req, res) => {
         res.end('ok');
       },
-      { port: 8080 }
+      { port: SERVER_PORT }
     );
 
     try {
@@ -2259,7 +2304,7 @@ describe('supports http with nodejs', () => {
               );
             });
           },
-          { port: 8080 }
+          { port: SERVER_PORT }
         );
 
         try {
@@ -2297,7 +2342,7 @@ describe('supports http with nodejs', () => {
               })
             );
           },
-          { port: 8080 }
+          { port: SERVER_PORT }
         );
 
         try {
@@ -2355,7 +2400,7 @@ describe('supports http with nodejs', () => {
           const expressServer = app.listen(0, () => resolve(expressServer));
           expressServer.on('error', reject);
         },
-        { port: 8080 }
+        { port: SERVER_PORT }
       );
 
       try {
@@ -2391,7 +2436,7 @@ describe('supports http with nodejs', () => {
         async (req, res) => {
           res.end(await getStream(req));
         },
-        { port: 8080 }
+        { port: SERVER_PORT }
       );
 
       try {
@@ -2433,7 +2478,7 @@ describe('supports http with nodejs', () => {
           const expressServer = app.listen(0, () => resolve(expressServer));
           expressServer.on('error', reject);
         },
-        { port: 8080 }
+        { port: SERVER_PORT }
       );
 
       try {
@@ -2475,7 +2520,7 @@ describe('supports http with nodejs', () => {
         (req, res) => {
           req.pipe(res);
         },
-        { port: 8080 }
+        { port: SERVER_PORT }
       );
 
       try {
@@ -2541,7 +2586,7 @@ describe('supports http with nodejs', () => {
           {
             rate: 100 * 1024,
           },
-          { port: 8080 }
+          { port: SERVER_PORT }
         );
 
         try {
@@ -2610,7 +2655,7 @@ describe('supports http with nodejs', () => {
           {
             rate: 100 * 1024,
           },
-          { port: 8080 }
+          { port: SERVER_PORT }
         );
 
         try {
@@ -2783,10 +2828,13 @@ describe('supports http with nodejs', () => {
 
   describe('request aborting', () => {
     it('should be able to abort the response stream', async () => {
-      const server = await startHTTPServer({
-        rate: 100000,
-        useBuffering: true,
-      });
+      const server = await startHTTPServer(
+        {
+          rate: 100000,
+          useBuffering: true,
+        },
+        { port: SERVER_PORT }
+      );
 
       try {
         const buf = Buffer.alloc(1024 * 1024);
@@ -2832,7 +2880,7 @@ describe('supports http with nodejs', () => {
   });
 
   it('should support function as paramsSerializer value', async () => {
-    const server = await startHTTPServer((req, res) => res.end(req.url));
+    const server = await startHTTPServer((req, res) => res.end(req.url), { port: SERVER_PORT });
 
     try {
       const { data } = await axios.post(`http://localhost:${server.address().port}`, 'test', {
@@ -2989,7 +3037,7 @@ describe('supports http with nodejs', () => {
             })
           );
         },
-        { port: 8080 }
+        { port: SERVER_PORT }
       );
 
       try {
@@ -3043,7 +3091,7 @@ describe('supports http with nodejs', () => {
         },
         {
           useHTTP2: true,
-          port: 8080,
+          port: SERVER_PORT,
         }
       );
 
@@ -3060,7 +3108,7 @@ describe('supports http with nodejs', () => {
     it('should support request payload', async () => {
       const server = await startHTTPServer(null, {
         useHTTP2: true,
-        port: 8080,
+        port: SERVER_PORT,
       });
 
       try {
@@ -3092,7 +3140,7 @@ describe('supports http with nodejs', () => {
         },
         {
           useHTTP2: true,
-          port: 8080,
+          port: SERVER_PORT,
         }
       );
 
@@ -3134,7 +3182,7 @@ describe('supports http with nodejs', () => {
             },
             {
               useHTTP2: true,
-              port: 8080,
+              port: SERVER_PORT,
             }
           );
 
@@ -3165,7 +3213,7 @@ describe('supports http with nodejs', () => {
         },
         {
           useHTTP2: true,
-          port: 8080,
+          port: SERVER_PORT,
         }
       );
 
@@ -3210,7 +3258,7 @@ describe('supports http with nodejs', () => {
         },
         {
           useHTTP2: true,
-          port: 8080,
+          port: SERVER_PORT,
         }
       );
 
@@ -3251,7 +3299,7 @@ describe('supports http with nodejs', () => {
         },
         {
           useHTTP2: true,
-          port: 8080,
+          port: SERVER_PORT,
         }
       );
 
@@ -3302,7 +3350,7 @@ describe('supports http with nodejs', () => {
           },
           {
             useHTTP2: true,
-            port: 8080,
+            port: SERVER_PORT,
           }
         );
 
@@ -3339,7 +3387,7 @@ describe('supports http with nodejs', () => {
           },
           {
             useHTTP2: true,
-            port: 8080,
+            port: SERVER_PORT,
           }
         );
 
@@ -3351,7 +3399,7 @@ describe('supports http with nodejs', () => {
           },
           {
             useHTTP2: true,
-            port: 8081,
+            port: ALTERNATE_SERVER_PORT,
           }
         );
 
@@ -3389,7 +3437,7 @@ describe('supports http with nodejs', () => {
           },
           {
             useHTTP2: true,
-            port: 8080,
+            port: SERVER_PORT,
           }
         );
 
@@ -3428,7 +3476,7 @@ describe('supports http with nodejs', () => {
           },
           {
             useHTTP2: true,
-            port: 8080,
+            port: SERVER_PORT,
           }
         );
 
@@ -3470,7 +3518,7 @@ describe('supports http with nodejs', () => {
           },
           {
             useHTTP2: true,
-            port: 8080,
+            port: SERVER_PORT,
           }
         );
 
@@ -3542,7 +3590,7 @@ describe('supports http with nodejs', () => {
 
           res.end('ok');
         },
-        { port: 8080 }
+        { port: SERVER_PORT }
       );
 
       try {

tests/unit/api.test.js

@@ -0,0 +1,97 @@
+import { describe, it } from 'vitest';
+import assert from 'assert';
+import axios from '../../index.js';
+
+describe('static api', () => {
+  it('should have request method helpers', () => {
+    assert.strictEqual(typeof axios.request, 'function');
+    assert.strictEqual(typeof axios.get, 'function');
+    assert.strictEqual(typeof axios.head, 'function');
+    assert.strictEqual(typeof axios.options, 'function');
+    assert.strictEqual(typeof axios.delete, 'function');
+    assert.strictEqual(typeof axios.post, 'function');
+    assert.strictEqual(typeof axios.put, 'function');
+    assert.strictEqual(typeof axios.patch, 'function');
+  });
+
+  it('should have promise method helpers', async () => {
+    const promise = axios.request({
+      url: '/test',
+      adapter: (config) =>
+        Promise.resolve({
+          data: null,
+          status: 200,
+          statusText: 'OK',
+          headers: {},
+          config,
+          request: {},
+        }),
+    });
+
+    assert.strictEqual(typeof promise.then, 'function');
+    assert.strictEqual(typeof promise.catch, 'function');
+
+    await promise;
+  });
+
+  it('should have defaults', () => {
+    assert.strictEqual(typeof axios.defaults, 'object');
+    assert.strictEqual(typeof axios.defaults.headers, 'object');
+  });
+
+  it('should have interceptors', () => {
+    assert.strictEqual(typeof axios.interceptors.request, 'object');
+    assert.strictEqual(typeof axios.interceptors.response, 'object');
+  });
+
+  it('should have all/spread helpers', () => {
+    assert.strictEqual(typeof axios.all, 'function');
+    assert.strictEqual(typeof axios.spread, 'function');
+  });
+
+  it('should have factory method', () => {
+    assert.strictEqual(typeof axios.create, 'function');
+  });
+
+  it('should have CanceledError, CancelToken, and isCancel properties', () => {
+    assert.strictEqual(typeof axios.Cancel, 'function');
+    assert.strictEqual(typeof axios.CancelToken, 'function');
+    assert.strictEqual(typeof axios.isCancel, 'function');
+  });
+
+  it('should have getUri method', () => {
+    assert.strictEqual(typeof axios.getUri, 'function');
+  });
+
+  it('should have isAxiosError properties', () => {
+    assert.strictEqual(typeof axios.isAxiosError, 'function');
+  });
+
+  it('should have mergeConfig properties', () => {
+    assert.strictEqual(typeof axios.mergeConfig, 'function');
+  });
+
+  it('should have getAdapter properties', () => {
+    assert.strictEqual(typeof axios.getAdapter, 'function');
+  });
+});
+
+describe('instance api', () => {
+  const instance = axios.create();
+
+  it('should have request methods', () => {
+    assert.strictEqual(typeof instance.request, 'function');
+    assert.strictEqual(typeof instance.get, 'function');
+    assert.strictEqual(typeof instance.options, 'function');
+    assert.strictEqual(typeof instance.head, 'function');
+    assert.strictEqual(typeof instance.delete, 'function');
+    assert.strictEqual(typeof instance.post, 'function');
+    assert.strictEqual(typeof instance.put, 'function');
+    assert.strictEqual(typeof instance.patch, 'function');
+  });
+
+  it('should have interceptors', () => {
+    assert.strictEqual(typeof instance.interceptors.request, 'object');
+    assert.strictEqual(typeof instance.interceptors.response, 'object');
+  });
+});

tests/unit/cancel/canceledError.test.js

@@ -0,0 +1,23 @@
+import { describe, it, expect } from 'vitest';
+import { isNativeError } from 'node:util/types';
+import CanceledError from '../../../lib/cancel/CanceledError.js';
+
+describe('cancel::CanceledError', () => {
+  describe('toString', () => {
+    it('returns the default message when message is not specified', () => {
+      const cancel = new CanceledError();
+
+      expect(cancel.toString()).toBe('CanceledError: canceled');
+    });
+
+    it('returns the provided message when message is specified', () => {
+      const cancel = new CanceledError('Operation has been canceled.');
+
+      expect(cancel.toString()).toBe('CanceledError: Operation has been canceled.');
+    });
+  });
+
+  it('is recognized as a native error by Node util/types', () => {
+    expect(isNativeError(new CanceledError('My Canceled Error'))).toBe(true);
+  });
+});

tests/unit/cancel/isCancel.test.js

@@ -0,0 +1,13 @@
+import { describe, it, expect } from 'vitest';
+import isCancel from '../../../lib/cancel/isCancel.js';
+import CanceledError from '../../../lib/cancel/CanceledError.js';
+
+describe('cancel::isCancel', () => {
+  it('returns true when value is a CanceledError', () => {
+    expect(isCancel(new CanceledError())).toBe(true);
+  });
+
+  it('returns false when value is not canceled', () => {
+    expect(isCancel({ foo: 'bar' })).toBe(false);
+  });
+});

tests/unit/core/AxiosError.test.js

@@ -0,0 +1,102 @@
+import { describe, it, expect } from 'vitest';
+import { isNativeError } from 'node:util/types';
+import AxiosError from '../../../lib/core/AxiosError.js';
+
+describe('core::AxiosError', () => {
+  it('creates an error with message, config, code, request, response, stack and isAxiosError', () => {
+    const request = { path: '/foo' };
+    const response = { status: 200, data: { foo: 'bar' } };
+    const error = new AxiosError('Boom!', 'ESOMETHING', { foo: 'bar' }, request, response);
+
+    expect(error).toBeInstanceOf(Error);
+    expect(error.message).toBe('Boom!');
+    expect(error.config).toEqual({ foo: 'bar' });
+    expect(error.code).toBe('ESOMETHING');
+    expect(error.request).toBe(request);
+    expect(error.response).toBe(response);
+    expect(error.isAxiosError).toBe(true);
+    expect(error.stack).toBeDefined();
+  });
+
+  it('serializes to JSON safely', () => {
+    // request/response are intentionally omitted from the serialized shape
+    // to avoid circular-reference problems.
+    const request = { path: '/foo' };
+    const response = { status: 200, data: { foo: 'bar' } };
+    const error = new AxiosError('Boom!', 'ESOMETHING', { foo: 'bar' }, request, response);
+    const json = error.toJSON();
+
+    expect(json.message).toBe('Boom!');
+    expect(json.config).toEqual({ foo: 'bar' });
+    expect(json.code).toBe('ESOMETHING');
+    expect(json.status).toBe(200);
+    expect(json.request).toBeUndefined();
+    expect(json.response).toBeUndefined();
+  });
+
+  describe('AxiosError.from', () => {
+    it('adds config, code, request and response to the wrapped error', () => {
+      const error = new Error('Boom!');
+      const request = { path: '/foo' };
+      const response = { status: 200, data: { foo: 'bar' } };
+
+      const axiosError = AxiosError.from(error, 'ESOMETHING', { foo: 'bar' }, request, response);
+
+      expect(axiosError.config).toEqual({ foo: 'bar' });
+      expect(axiosError.code).toBe('ESOMETHING');
+      expect(axiosError.request).toBe(request);
+      expect(axiosError.response).toBe(response);
+      expect(axiosError.isAxiosError).toBe(true);
+    });
+
+    it('returns an AxiosError instance', () => {
+      const axiosError = AxiosError.from(new Error('Boom!'), 'ESOMETHING', { foo: 'bar' });
+
+      expect(axiosError).toBeInstanceOf(AxiosError);
+    });
+
+    it('preserves status from the original error when response is not provided', () => {
+      const error = new Error('Network Error');
+      error.status = 404;
+
+      const axiosError = AxiosError.from(error, 'ERR_NETWORK', { foo: 'bar' });
+
+      expect(axiosError.status).toBe(404);
+    });
+
+    it('prefers response.status over error.status when response is provided', () => {
+      const error = new Error('Error');
+      error.status = 500;
+      const response = { status: 404 };
+
+      const axiosError = AxiosError.from(error, 'ERR_BAD_REQUEST', {}, null, response);
+
+      expect(axiosError.status).toBe(404);
+    });
+  });
+
+  it('is recognized as a native error by Node util/types', () => {
+    expect(isNativeError(new AxiosError('My Axios Error'))).toBe(true);
+  });
+
+  it('supports static error-code properties', () => {
+    const error = new AxiosError('My Axios Error', AxiosError.ECONNABORTED);
+
+    expect(error.code).toBe(AxiosError.ECONNABORTED);
+  });
+
+  it('sets status when response is passed to constructor', () => {
+    const error = new AxiosError('test', 'foo', {}, {}, { status: 400 });
+
+    expect(error.status).toBe(400);
+  });
+
+  it('keeps message enumerable for backward compatibility', () => {
+    const error = new AxiosError('Test error message', 'ERR_TEST', { foo: 'bar' });
+
+    expect(Object.keys(error)).toContain('message');
+    expect(Object.entries(error).find(([key]) => key === 'message')?.[1]).toBe('Test error message');
+    expect({ ...error }.message).toBe('Test error message');
+    expect(Object.getOwnPropertyDescriptor(error, 'message')?.enumerable).toBe(true);
+  });
+});

tests/unit/core/buildFullPath.test.js

@@ -0,0 +1,34 @@
+import { describe, it, expect } from 'vitest';
+import buildFullPath from '../../../lib/core/buildFullPath.js';
+
+describe('core::buildFullPath', () => {
+  it('combines URLs when the requested URL is relative', () => {
+    expect(buildFullPath('https://api.github.com', '/users')).toBe('https://api.github.com/users');
+  });
+
+  it('does not combine URLs when the requested URL is absolute', () => {
+    expect(buildFullPath('https://api.github.com', 'https://api.example.com/users')).toBe(
+      'https://api.example.com/users'
+    );
+  });
+
+  it('combines URLs when requested URL is absolute and allowAbsoluteUrls is false', () => {
+    expect(buildFullPath('https://api.github.com', 'https://api.example.com/users', false)).toBe(
+      'https://api.github.com/https://api.example.com/users'
+    );
+  });
+
+  it('does not combine URLs when baseURL is missing and allowAbsoluteUrls is false', () => {
+    expect(buildFullPath(undefined, 'https://api.example.com/users', false)).toBe(
+      'https://api.example.com/users'
+    );
+  });
+
+  it('does not combine URLs when baseURL is not configured', () => {
+    expect(buildFullPath(undefined, '/users')).toBe('/users');
+  });
+
+  it('combines URLs when baseURL and requested URL are both relative', () => {
+    expect(buildFullPath('/api', '/users')).toBe('/api/users');
+  });
+});

tests/unit/core/mergeConfig.test.js

@@ -0,0 +1,357 @@
+import { describe, it, expect } from 'vitest';
+import defaults from '../../../lib/defaults/index.js';
+import mergeConfig from '../../../lib/core/mergeConfig.js';
+import { AxiosHeaders } from '../../../index.js';
+
+describe('core::mergeConfig', () => {
+  it('accepts undefined for second argument', () => {
+    expect(mergeConfig(defaults, undefined)).toEqual(defaults);
+  });
+
+  it('accepts an object for second argument', () => {
+    expect(mergeConfig(defaults, {})).toEqual(defaults);
+  });
+
+  it('does not leave references', () => {
+    const merged = mergeConfig(defaults, {});
+
+    expect(merged).not.toBe(defaults);
+    expect(merged.headers).not.toBe(defaults.headers);
+  });
+
+  it('allows setting request options', () => {
+    const config = {
+      url: '__sample url__',
+      method: '__sample method__',
+      params: '__sample params__',
+      data: { foo: true },
+    };
+    const merged = mergeConfig(defaults, config);
+
+    expect(merged.url).toBe(config.url);
+    expect(merged.method).toBe(config.method);
+    expect(merged.params).toBe(config.params);
+    expect(merged.data).toEqual(config.data);
+  });
+
+  it('does not inherit request options', () => {
+    const localDefaults = {
+      method: '__sample method__',
+      data: { foo: true },
+    };
+    const merged = mergeConfig(localDefaults, {});
+
+    expect(merged.method).toBeUndefined();
+    expect(merged.data).toBeUndefined();
+  });
+
+  for (const key of ['auth', 'headers', 'params', 'proxy']) {
+    it(`sets new config for ${key} without default`, () => {
+      const config1 = { [key]: undefined };
+      const config2 = { [key]: { user: 'foo', pass: 'test' } };
+      const expected = { [key]: { user: 'foo', pass: 'test' } };
+
+      expect(mergeConfig(config1, config2)).toEqual(expected);
+    });
+
+    it(`merges ${key} with defaults`, () => {
+      const config1 = { [key]: { user: 'foo', pass: 'bar' } };
+      const config2 = { [key]: { pass: 'test' } };
+      const expected = { [key]: { user: 'foo', pass: 'test' } };
+
+      expect(mergeConfig(config1, config2)).toEqual(expected);
+    });
+
+    it.each([false, null, 123])(`overwrites default ${key} with %p`, (value) => {
+      const config1 = { [key]: { user: 'foo', pass: 'test' } };
+      const config2 = { [key]: value };
+      const expected = { [key]: value };
+
+      expect(mergeConfig(config1, config2)).toEqual(expected);
+    });
+  }
+
+  it('allows setting other options', () => {
+    const merged = mergeConfig(defaults, { timeout: 123 });
+
+    expect(merged.timeout).toBe(123);
+  });
+
+  it('allows setting custom options', () => {
+    const merged = mergeConfig(defaults, { foo: 'bar' });
+
+    expect(merged.foo).toBe('bar');
+  });
+
+  it('allows setting custom default options', () => {
+    const merged = mergeConfig({ foo: 'bar' }, {});
+
+    expect(merged.foo).toBe('bar');
+  });
+
+  it('allows merging custom objects in config', () => {
+    const merged = mergeConfig(
+      {
+        nestedConfig: {
+          propertyOnDefaultConfig: true,
+        },
+      },
+      {
+        nestedConfig: {
+          propertyOnRequestConfig: true,
+        },
+      }
+    );
+
+    expect(merged.nestedConfig.propertyOnDefaultConfig).toBe(true);
+    expect(merged.nestedConfig.propertyOnRequestConfig).toBe(true);
+  });
+
+  describe('headers', () => {
+    it('allows merging with AxiosHeaders instances', () => {
+      const merged = mergeConfig(
+        {
+          headers: new AxiosHeaders({
+            x: 1,
+            y: 2,
+          }),
+        },
+        {
+          headers: new AxiosHeaders({
+            X: 1,
+            Y: 2,
+          }),
+        }
+      );
+
+      expect(merged.headers).toEqual({
+        x: '1',
+        y: '2',
+      });
+    });
+  });
+
+  describe('valueFromConfig2Keys', () => {
+    const config1 = { url: '/foo', method: 'post', data: { a: 3 } };
+
+    it('skips if config2 does not define the key', () => {
+      expect(mergeConfig(config1, {})).toEqual({});
+    });
+
+    it('clones config2 when it is a plain object', () => {
+      const data = { a: 1, b: 2 };
+      const merged = mergeConfig(config1, { data });
+
+      expect(merged.data).toEqual(data);
+      expect(merged.data).not.toBe(data);
+    });
+
+    it('clones config2 when it is an array', () => {
+      const data = [1, 2, 3];
+      const merged = mergeConfig(config1, { data });
+
+      expect(merged.data).toEqual(data);
+      expect(merged.data).not.toBe(data);
+    });
+
+    it('sets config2 value directly for non-mergeable values', () => {
+      const obj = Object.create({});
+
+      expect(mergeConfig(config1, { data: 1 }).data).toBe(1);
+      expect(mergeConfig(config1, { data: 'str' }).data).toBe('str');
+      expect(mergeConfig(config1, { data: obj }).data).toBe(obj);
+      expect(mergeConfig(config1, { data: null }).data).toBe(null);
+    });
+  });
+
+  describe('mergeDeepPropertiesKeys', () => {
+    it('skips when both config1 and config2 values are undefined', () => {
+      expect(mergeConfig({ headers: undefined }, { headers: undefined })).toEqual({});
+    });
+
+    it('merges when both values are plain objects', () => {
+      expect(mergeConfig({ headers: { a: 1, b: 1 } }, { headers: { b: 2, c: 2 } })).toEqual({
+        headers: { a: 1, b: 2, c: 2 },
+      });
+    });
+
+    it('clones config2 when it is a plain object', () => {
+      const config1 = { headers: [1, 2, 3] };
+      const config2 = { headers: { a: 1, b: 2 } };
+      const merged = mergeConfig(config1, config2);
+
+      expect(merged.headers).toEqual(config2.headers);
+      expect(merged.headers).not.toBe(config2.headers);
+    });
+
+    it('clones config2 when it is an array', () => {
+      const config1 = { headers: { a: 1, b: 1 } };
+      const config2 = { headers: [1, 2, 3] };
+      const merged = mergeConfig(config1, config2);
+
+      expect(merged.headers).toEqual(config2.headers);
+      expect(merged.headers).not.toBe(config2.headers);
+    });
+
+    it('sets config2 value directly for non-mergeable values', () => {
+      const config1 = { headers: { a: 1, b: 1 } };
+      const obj = Object.create({});
+
+      expect(mergeConfig(config1, { headers: 1 }).headers).toBe(1);
+      expect(mergeConfig(config1, { headers: 'str' }).headers).toBe('str');
+      expect(mergeConfig(config1, { headers: obj }).headers).toBe(obj);
+      expect(mergeConfig(config1, { headers: null }).headers).toBe(null);
+    });
+
+    it('clones config1 when it is a plain object', () => {
+      const config1 = { headers: { a: 1, b: 2 } };
+      const merged = mergeConfig(config1, {});
+
+      expect(merged.headers).toEqual(config1.headers);
+      expect(merged.headers).not.toBe(config1.headers);
+    });
+
+    it('clones config1 when it is an array', () => {
+      const config1 = { headers: [1, 2, 3] };
+      const merged = mergeConfig(config1, {});
+
+      expect(merged.headers).toEqual(config1.headers);
+      expect(merged.headers).not.toBe(config1.headers);
+    });
+
+    it('sets config1 value directly for non-mergeable values', () => {
+      const obj = Object.create({});
+
+      expect(mergeConfig({ headers: 1 }, {}).headers).toBe(1);
+      expect(mergeConfig({ headers: 'str' }, {}).headers).toBe('str');
+      expect(mergeConfig({ headers: obj }, {}).headers).toBe(obj);
+      expect(mergeConfig({ headers: null }, {}).headers).toBe(null);
+    });
+  });
+
+  describe('defaultToConfig2Keys', () => {
+    it('skips when both config1 and config2 values are undefined', () => {
+      expect(mergeConfig({ transformRequest: undefined }, { transformRequest: undefined })).toEqual(
+        {}
+      );
+    });
+
+    it('clones config2 when both values are plain objects', () => {
+      const config1 = { transformRequest: { a: 1, b: 1 } };
+      const config2 = { transformRequest: { b: 2, c: 2 } };
+      const merged = mergeConfig(config1, config2);
+
+      expect(merged.transformRequest).toEqual(config2.transformRequest);
+      expect(merged.transformRequest).not.toBe(config2.transformRequest);
+    });
+
+    it('clones config2 when it is an array', () => {
+      const config1 = { transformRequest: { a: 1, b: 1 } };
+      const config2 = { transformRequest: [1, 2, 3] };
+      const merged = mergeConfig(config1, config2);
+
+      expect(merged.transformRequest).toEqual(config2.transformRequest);
+      expect(merged.transformRequest).not.toBe(config2.transformRequest);
+    });
+
+    it('sets config2 value directly for non-mergeable values', () => {
+      const config1 = { transformRequest: { a: 1, b: 1 } };
+      const obj = Object.create({});
+
+      expect(mergeConfig(config1, { transformRequest: 1 }).transformRequest).toBe(1);
+      expect(mergeConfig(config1, { transformRequest: 'str' }).transformRequest).toBe('str');
+      expect(mergeConfig(config1, { transformRequest: obj }).transformRequest).toBe(obj);
+      expect(mergeConfig(config1, { transformRequest: null }).transformRequest).toBe(null);
+    });
+
+    it('clones config1 when it is a plain object', () => {
+      const config1 = { transformRequest: { a: 1, b: 2 } };
+      const merged = mergeConfig(config1, {});
+
+      expect(merged.transformRequest).toEqual(config1.transformRequest);
+      expect(merged.transformRequest).not.toBe(config1.transformRequest);
+    });
+
+    it('clones config1 when it is an array', () => {
+      const config1 = { transformRequest: [1, 2, 3] };
+      const merged = mergeConfig(config1, {});
+
+      expect(merged.transformRequest).toEqual(config1.transformRequest);
+      expect(merged.transformRequest).not.toBe(config1.transformRequest);
+    });
+
+    it('sets config1 value directly for non-mergeable values', () => {
+      const obj = Object.create({});
+
+      expect(mergeConfig({ transformRequest: 1 }, {}).transformRequest).toBe(1);
+      expect(mergeConfig({ transformRequest: 'str' }, {}).transformRequest).toBe('str');
+      expect(mergeConfig({ transformRequest: obj }, {}).transformRequest).toBe(obj);
+      expect(mergeConfig({ transformRequest: null }, {}).transformRequest).toBe(null);
+    });
+  });
+
+  describe('directMergeKeys', () => {
+    it('merges when config2 defines the key', () => {
+      expect(mergeConfig({}, { validateStatus: undefined })).toEqual({ validateStatus: undefined });
+    });
+
+    it('merges when both values are plain objects', () => {
+      expect(
+        mergeConfig({ validateStatus: { a: 1, b: 1 } }, { validateStatus: { b: 2, c: 2 } })
+      ).toEqual({ validateStatus: { a: 1, b: 2, c: 2 } });
+    });
+
+    it('clones config2 when it is a plain object', () => {
+      const config1 = { validateStatus: [1, 2, 3] };
+      const config2 = { validateStatus: { a: 1, b: 2 } };
+      const merged = mergeConfig(config1, config2);
+
+      expect(merged.validateStatus).toEqual(config2.validateStatus);
+      expect(merged.validateStatus).not.toBe(config2.validateStatus);
+    });
+
+    it('clones config2 when it is an array', () => {
+      const config1 = { validateStatus: { a: 1, b: 2 } };
+      const config2 = { validateStatus: [1, 2, 3] };
+      const merged = mergeConfig(config1, config2);
+
+      expect(merged.validateStatus).toEqual(config2.validateStatus);
+      expect(merged.validateStatus).not.toBe(config2.validateStatus);
+    });
+
+    it('sets config2 value directly for non-mergeable values', () => {
+      const config1 = { validateStatus: { a: 1, b: 2 } };
+      const obj = Object.create({});
+
+      expect(mergeConfig(config1, { validateStatus: 1 }).validateStatus).toBe(1);
+      expect(mergeConfig(config1, { validateStatus: 'str' }).validateStatus).toBe('str');
+      expect(mergeConfig(config1, { validateStatus: obj }).validateStatus).toBe(obj);
+      expect(mergeConfig(config1, { validateStatus: null }).validateStatus).toBe(null);
+    });
+
+    it('clones config1 when it is a plain object', () => {
+      const config1 = { validateStatus: { a: 1, b: 2 } };
+      const merged = mergeConfig(config1, {});
+
+      expect(merged.validateStatus).toEqual(config1.validateStatus);
+      expect(merged.validateStatus).not.toBe(config1.validateStatus);
+    });
+
+    it('clones config1 when it is an array', () => {
+      const config1 = { validateStatus: [1, 2, 3] };
+      const merged = mergeConfig(config1, {});
+
+      expect(merged.validateStatus).toEqual(config1.validateStatus);
+      expect(merged.validateStatus).not.toBe(config1.validateStatus);
+    });
+
+    it('sets config1 value directly for non-mergeable values', () => {
+      const obj = Object.create({});
+
+      expect(mergeConfig({ validateStatus: 1 }, {}).validateStatus).toBe(1);
+      expect(mergeConfig({ validateStatus: 'str' }, {}).validateStatus).toBe('str');
+      expect(mergeConfig({ validateStatus: obj }, {}).validateStatus).toBe(obj);
+      expect(mergeConfig({ validateStatus: null }, {}).validateStatus).toBe(null);
+    });
+  });
+});

tests/unit/core/transformData.test.js

@@ -0,0 +1,49 @@
+import { describe, it, expect } from 'vitest';
+import transformData from '../../../lib/core/transformData.js';
+
+describe('core::transformData', () => {
+  it('supports a single transformer', () => {
+    const data = transformData.call({}, (value) => {
+      value = 'foo';
+      return value;
+    });
+
+    expect(data).toBe('foo');
+  });
+
+  it('supports an array of transformers', () => {
+    const data = transformData.call({ data: '' }, [
+      (value) => value + 'f',
+      (value) => value + 'o',
+      (value) => value + 'o',
+    ]);
+
+    expect(data).toBe('foo');
+  });
+
+  it('passes headers through to transformers', () => {
+    const headers = {
+      'content-type': 'foo/bar',
+    };
+
+    const data = transformData.call(
+      {
+        data: '',
+        headers,
+      },
+      [(value, currentHeaders) => value + currentHeaders['content-type']]
+    );
+
+    expect(data).toBe('foo/bar');
+  });
+
+  it('passes status code through to transformers', () => {
+    const data = transformData.call(
+      {},
+      [(value, _headers, status) => value + status],
+      { data: '', status: 200 }
+    );
+
+    expect(data).toBe('200');
+  });
+});

tests/unit/helpers/bind.test.js

@@ -0,0 +1,13 @@
+import { describe, it, expect } from 'vitest';
+import bind from '../../../lib/helpers/bind.js';
+
+describe('bind', () => {
+  it('should bind an object to a function', () => {
+    const o = { val: 123 };
+    const f = bind(function (num) {
+      return this.val * num;
+    }, o);
+
+    expect(f(2)).toEqual(246);
+  });
+});

tests/unit/helpers/buildURL.test.js

@@ -0,0 +1,126 @@
+import { describe, it, expect, vi } from 'vitest';
+import buildURL from '../../../lib/helpers/buildURL.js';
+
+describe('helpers::buildURL', () => {
+  it('should support null params', () => {
+    expect(buildURL('/foo')).toEqual('/foo');
+  });
+
+  it('should support params', () => {
+    expect(
+      buildURL('/foo', {
+        foo: 'bar',
+        isUndefined: undefined,
+        isNull: null,
+      })
+    ).toEqual('/foo?foo=bar');
+  });
+
+  it('should support sending raw params to custom serializer func', () => {
+    const serializer = vi.fn().mockReturnValue('foo=bar');
+    const params = { foo: 'bar' };
+    const options = {
+      serialize: serializer,
+    };
+    expect(
+      buildURL(
+        '/foo',
+        {
+          foo: 'bar',
+        },
+        options
+      )
+    ).toEqual('/foo?foo=bar');
+    expect(serializer).toHaveBeenCalledTimes(1);
+    expect(serializer).toHaveBeenCalledWith(params, options);
+  });
+
+  it('should support object params', () => {
+    expect(
+      buildURL('/foo', {
+        foo: {
+          bar: 'baz',
+        },
+      })
+    ).toEqual('/foo?foo%5Bbar%5D=baz');
+  });
+
+  it('should support date params', () => {
+    const date = new Date();
+
+    expect(
+      buildURL('/foo', {
+        date,
+      })
+    ).toEqual('/foo?date=' + date.toISOString());
+  });
+
+  it('should support array params with encode', () => {
+    expect(
+      buildURL('/foo', {
+        foo: ['bar', 'baz'],
+      })
+    ).toEqual('/foo?foo%5B%5D=bar&foo%5B%5D=baz');
+  });
+
+  it('should support special char params', () => {
+    expect(
+      buildURL('/foo', {
+        foo: ':$, ',
+      })
+    ).toEqual('/foo?foo=:$,+');
+  });
+
+  it('should support existing params', () => {
+    expect(
+      buildURL('/foo?foo=bar', {
+        bar: 'baz',
+      })
+    ).toEqual('/foo?foo=bar&bar=baz');
+  });
+
+  it('should support "length" parameter', () => {
+    expect(
+      buildURL('/foo', {
+        query: 'bar',
+        start: 0,
+        length: 5,
+      })
+    ).toEqual('/foo?query=bar&start=0&length=5');
+  });
+
+  it('should correct discard url hash mark', () => {
+    expect(
+      buildURL('/foo?foo=bar#hash', {
+        query: 'baz',
+      })
+    ).toEqual('/foo?foo=bar&query=baz');
+  });
+
+  it('should support URLSearchParams', () => {
+    expect(buildURL('/foo', new URLSearchParams('bar=baz'))).toEqual('/foo?bar=baz');
+  });
+
+  it('should support custom serialize function', () => {
+    const params = {
+      x: 1,
+    };
+
+    const options = {
+      serialize: (thisParams, thisOptions) => {
+        expect(thisParams).toEqual(params);
+        expect(thisOptions).toEqual(options);
+        return 'rendered';
+      },
+    };
+
+    expect(buildURL('/foo', params, options)).toEqual('/foo?rendered');
+
+    const customSerializer = (thisParams) => {
+      expect(thisParams).toEqual(params);
+      return 'rendered';
+    };
+
+    expect(buildURL('/foo', params, customSerializer)).toEqual('/foo?rendered');
+  });
+});

tests/unit/helpers/combineURLs.test.js

@@ -0,0 +1,24 @@
+import { describe, it, expect } from 'vitest';
+import combineURLs from '../../../lib/helpers/combineURLs.js';
+
+describe('helpers::combineURLs', () => {
+  it('should combine URLs', () => {
+    expect(combineURLs('https://api.github.com', '/users')).toBe('https://api.github.com/users');
+  });
+
+  it('should remove duplicate slashes', () => {
+    expect(combineURLs('https://api.github.com/', '/users')).toBe('https://api.github.com/users');
+  });
+
+  it('should insert missing slash', () => {
+    expect(combineURLs('https://api.github.com', 'users')).toBe('https://api.github.com/users');
+  });
+
+  it('should not insert slash when relative url missing/empty', () => {
+    expect(combineURLs('https://api.github.com/users', '')).toBe('https://api.github.com/users');
+  });
+
+  it('should allow a single slash for relative url', () => {
+    expect(combineURLs('https://api.github.com/users', '/')).toBe('https://api.github.com/users/');
+  });
+});

tests/unit/helpers/formDataToJSON.test.js

@@ -0,0 +1,72 @@
+import { describe, it, expect } from 'vitest';
+import formDataToJSON from '../../../lib/helpers/formDataToJSON.js';
+
+describe('formDataToJSON', () => {
+  it('should convert a FormData Object to JSON Object', () => {
+    const formData = new FormData();
+
+    formData.append('foo[bar][baz]', '123');
+
+    expect(formDataToJSON(formData)).toEqual({
+      foo: {
+        bar: {
+          baz: '123',
+        },
+      },
+    });
+  });
+
+  it('should convert repeatable values as an array', () => {
+    const formData = new FormData();
+
+    formData.append('foo', '1');
+    formData.append('foo', '2');
+
+    expect(formDataToJSON(formData)).toEqual({
+      foo: ['1', '2'],
+    });
+  });
+
+  it('should convert props with empty brackets to arrays', () => {
+    const formData = new FormData();
+
+    formData.append('foo[]', '1');
+    formData.append('foo[]', '2');
+
+    expect(formDataToJSON(formData)).toEqual({
+      foo: ['1', '2'],
+    });
+  });
+
+  it('should supported indexed arrays', () => {
+    const formData = new FormData();
+
+    formData.append('foo[0]', '1');
+    formData.append('foo[1]', '2');
+
+    expect(formDataToJSON(formData)).toEqual({
+      foo: ['1', '2'],
+    });
+  });
+
+  it('should resist prototype pollution CVE', () => {
+    const formData = new FormData();
+
+    formData.append('foo[0]', '1');
+    formData.append('foo[1]', '2');
+    formData.append('__proto__.x', 'hack');
+    formData.append('constructor.prototype.y', 'value');
+
+    expect(formDataToJSON(formData)).toEqual({
+      foo: ['1', '2'],
+      constructor: {
+        prototype: {
+          y: 'value',
+        },
+      },
+    });
+
+    expect({}.x).toEqual(undefined);
+    expect({}.y).toEqual(undefined);
+  });
+});

tests/unit/helpers/isAbsoluteURL.test.js

@@ -0,0 +1,24 @@
+import { describe, it, expect } from 'vitest';
+import isAbsoluteURL from '../../../lib/helpers/isAbsoluteURL.js';
+
+describe('helpers::isAbsoluteURL', () => {
+  it('should return true if URL begins with valid scheme name', () => {
+    expect(isAbsoluteURL('https://api.github.com/users')).toBe(true);
+    expect(isAbsoluteURL('custom-scheme-v1.0://example.com/')).toBe(true);
+    expect(isAbsoluteURL('HTTP://example.com/')).toBe(true);
+  });
+
+  it('should return false if URL begins with invalid scheme name', () => {
+    expect(isAbsoluteURL('123://example.com/')).toBe(false);
+    expect(isAbsoluteURL('!valid://example.com/')).toBe(false);
+  });
+
+  it('should return true if URL is protocol-relative', () => {
+    expect(isAbsoluteURL('//example.com/')).toBe(true);
+  });
+
+  it('should return false if URL is relative', () => {
+    expect(isAbsoluteURL('/foo')).toBe(false);
+    expect(isAbsoluteURL('foo')).toBe(false);
+  });
+});

tests/unit/helpers/isAxiosError.test.js

@@ -0,0 +1,21 @@
+import { describe, it, expect } from 'vitest';
+import AxiosError from '../../../lib/core/AxiosError.js';
+import isAxiosError from '../../../lib/helpers/isAxiosError.js';
+
+describe('helpers::isAxiosError', () => {
+  it('should return true if the error is created by core::createError', () => {
+    expect(isAxiosError(new AxiosError('Boom!', null, { foo: 'bar' }))).toBe(true);
+  });
+
+  it('should return true if the error is enhanced by core::enhanceError', () => {
+    expect(isAxiosError(AxiosError.from(new Error('Boom!'), null, { foo: 'bar' }))).toBe(true);
+  });
+
+  it('should return false if the error is a normal Error instance', () => {
+    expect(isAxiosError(new Error('Boom!'))).toBe(false);
+  });
+
+  it('should return false if the error is null', () => {
+    expect(isAxiosError(null)).toBe(false);
+  });
+});

tests/unit/helpers/parseHeaders.test.js

@@ -0,0 +1,43 @@
+import { describe, it, expect } from 'vitest';
+import parseHeaders from '../../../lib/helpers/parseHeaders.js';
+
+describe('helpers::parseHeaders', () => {
+  it('should parse headers', () => {
+    const date = new Date();
+    const parsed = parseHeaders(
+      'Date: ' +
+        date.toISOString() +
+        '\n' +
+        'Content-Type: application/json\n' +
+        'Connection: keep-alive\n' +
+        'Transfer-Encoding: chunked'
+    );
+
+    expect(parsed.date).toEqual(date.toISOString());
+    expect(parsed['content-type']).toEqual('application/json');
+    expect(parsed.connection).toEqual('keep-alive');
+    expect(parsed['transfer-encoding']).toEqual('chunked');
+  });
+
+  it('should use array for set-cookie', () => {
+    const parsedZero = parseHeaders('');
+    const parsedSingle = parseHeaders('Set-Cookie: key=val;');
+    const parsedMulti = parseHeaders('Set-Cookie: key=val;\n' + 'Set-Cookie: key2=val2;\n');
+
+    expect(parsedZero['set-cookie']).toBeUndefined();
+    expect(parsedSingle['set-cookie']).toEqual(['key=val;']);
+    expect(parsedMulti['set-cookie']).toEqual(['key=val;', 'key2=val2;']);
+  });
+
+  it('should handle duplicates', () => {
+    const parsed = parseHeaders(
+      'Age: age-a\n' +
+        'Age: age-b\n' +
+        'Foo: foo-a\n' +
+        'Foo: foo-b\n'
+    );
+
+    expect(parsed.age).toEqual('age-a');
+    expect(parsed.foo).toEqual('foo-a, foo-b');
+  });
+});

tests/unit/helpers/spread.test.js

@@ -0,0 +1,21 @@
+import { describe, it, expect } from 'vitest';
+import spread from '../../../lib/helpers/spread.js';
+
+describe('helpers::spread', () => {
+  it('should spread array to arguments', () => {
+    let value = 0;
+    spread((a, b) => {
+      value = a * b;
+    })([5, 10]);
+
+    expect(value).toEqual(50);
+  });
+
+  it('should return callback result', () => {
+    const value = spread((a, b) => {
+      return a * b;
+    })([5, 10]);
+
+    expect(value).toEqual(50);
+  });
+});

tests/unit/helpers/validator.test.js

@@ -0,0 +1,67 @@
+import { describe, it, expect } from 'vitest';
+import AxiosError from '../../../lib/core/AxiosError.js';
+import validator from '../../../lib/helpers/validator.js';
+
+describe('validator::assertOptions', () => {
+  it('should throw only if unknown an option was passed', () => {
+    let error;
+    try {
+      validator.assertOptions(
+        {
+          x: true,
+        },
+        {
+          y: validator.validators.boolean,
+        }
+      );
+    } catch (err) {
+      error = err;
+    }
+    expect(error).toBeInstanceOf(AxiosError);
+    expect(error.message).toBe('Unknown option x');
+    expect(error.code).toBe(AxiosError.ERR_BAD_OPTION);
+
+    expect(() => {
+      validator.assertOptions(
+        {
+          x: true,
+        },
+        {
+          x: validator.validators.boolean,
+          y: validator.validators.boolean,
+        }
+      );
+    }).not.toThrow(new Error('Unknown option x'));
+  });
+
+  it("should throw TypeError only if option type doesn't match", () => {
+    let error;
+    try {
+      validator.assertOptions(
+        {
+          x: 123,
+        },
+        {
+          x: validator.validators.boolean,
+        }
+      );
+    } catch (err) {
+      error = err;
+    }
+    expect(error).toBeInstanceOf(AxiosError);
+    expect(error.message).toBe('option x must be a boolean');
+    expect(error.code).toBe(AxiosError.ERR_BAD_OPTION_VALUE);
+
+    expect(() => {
+      validator.assertOptions(
+        {
+          x: true,
+        },
+        {
+          x: validator.validators.boolean,
+          y: validator.validators.boolean,
+        }
+      );
+    }).not.toThrow();
+  });
+});

tests/unit/utils/endsWith.test.js

@@ -0,0 +1,13 @@
+import { describe, it, expect } from 'vitest';
+import utils from '../../../lib/utils.js';
+
+const { kindOf } = utils;
+
+describe('utils::kindOf', () => {
+  it('should return object tag', () => {
+    expect(kindOf({})).toEqual('object');
+    // cached result
+    expect(kindOf({})).toEqual('object');
+    expect(kindOf([])).toEqual('array');
+  });
+});

tests/unit/utils/extend.test.js

@@ -0,0 +1,40 @@
+import { describe, it, expect } from 'vitest';
+import utils from '../../../lib/utils.js';
+
+const { extend } = utils;
+
+describe('utils::extend', () => {
+  it('should be mutable', () => {
+    const a = {};
+    const b = { foo: 123 };
+
+    extend(a, b);
+
+    expect(a.foo).toEqual(b.foo);
+  });
+
+  it('should extend properties', () => {
+    let a = { foo: 123, bar: 456 };
+    const b = { bar: 789 };
+
+    a = extend(a, b);
+
+    expect(a.foo).toEqual(123);
+    expect(a.bar).toEqual(789);
+  });
+
+  it('should bind to thisArg', () => {
+    const a = {};
+    const b = {
+      getFoo: function getFoo() {
+        return this.foo;
+      },
+    };
+    const thisArg = { foo: 'barbaz' };
+
+    extend(a, b, thisArg);
+
+    expect(typeof a.getFoo).toEqual('function');
+    expect(a.getFoo()).toEqual(thisArg.foo);
+  });
+});

tests/unit/utils/forEach.test.js

@@ -0,0 +1,69 @@
+import { describe, it, expect } from 'vitest';
+import utils from '../../../lib/utils.js';
+
+const { forEach } = utils;
+
+describe('utils::forEach', () => {
+  it('should loop over an array', () => {
+    let sum = 0;
+
+    forEach([1, 2, 3, 4, 5], (val) => {
+      sum += val;
+    });
+
+    expect(sum).toEqual(15);
+  });
+
+  it('should loop over object keys', () => {
+    let keys = '';
+    let vals = 0;
+    const obj = {
+      b: 1,
+      a: 2,
+      r: 3,
+    };
+
+    forEach(obj, (v, k) => {
+      keys += k;
+      vals += v;
+    });
+
+    expect(keys).toEqual('bar');
+    expect(vals).toEqual(6);
+  });
+
+  it('should handle undefined gracefully', () => {
+    let count = 0;
+
+    forEach(undefined, () => {
+      count++;
+    });
+
+    expect(count).toEqual(0);
+  });
+
+  it('should make an array out of non-array argument', () => {
+    let count = 0;
+
+    forEach(
+      () => {},
+      () => {
+        count++;
+      }
+    );
+
+    expect(count).toEqual(1);
+  });
+
+  it('should handle non object prototype gracefully', () => {
+    let count = 0;
+    const data = Object.create(null);
+    data.foo = 'bar';
+
+    forEach(data, () => {
+      count++;
+    });
+
+    expect(count).toEqual(1);
+  });
+});

tests/unit/utils/isX.test.js

@@ -0,0 +1,80 @@
+import { describe, it, expect } from 'vitest';
+import utils from '../../../lib/utils.js';
+
+describe('utils::isX', () => {
+  it('should validate Array', () => {
+    expect(utils.isArray([])).toEqual(true);
+    expect(utils.isArray({ length: 5 })).toEqual(false);
+  });
+
+  it('should validate ArrayBuffer', () => {
+    expect(utils.isArrayBuffer(new ArrayBuffer(2))).toEqual(true);
+    expect(utils.isArrayBuffer({})).toEqual(false);
+  });
+
+  it('should validate ArrayBufferView', () => {
+    expect(utils.isArrayBufferView(new DataView(new ArrayBuffer(2)))).toEqual(true);
+  });
+
+  it('should validate FormData', () => {
+    expect(utils.isFormData(new FormData())).toEqual(true);
+  });
+
+  it('should validate Blob', () => {
+    expect(utils.isBlob(new Blob())).toEqual(true);
+  });
+
+  it('should validate String', () => {
+    expect(utils.isString('')).toEqual(true);
+    expect(
+      utils.isString({
+        toString: function () {
+          return '';
+        },
+      })
+    ).toEqual(false);
+  });
+
+  it('should validate Number', () => {
+    expect(utils.isNumber(123)).toEqual(true);
+    expect(utils.isNumber('123')).toEqual(false);
+  });
+
+  it('should validate Undefined', () => {
+    expect(utils.isUndefined()).toEqual(true);
+    expect(utils.isUndefined(null)).toEqual(false);
+  });
+
+  it('should validate Object', () => {
+    expect(utils.isObject({})).toEqual(true);
+    expect(utils.isObject([])).toEqual(true);
+    expect(utils.isObject(null)).toEqual(false);
+  });
+
+  it('should validate plain Object', () => {
+    expect(utils.isPlainObject({})).toEqual(true);
+    expect(utils.isPlainObject([])).toEqual(false);
+    expect(utils.isPlainObject(null)).toEqual(false);
+    expect(utils.isPlainObject(Object.create({}))).toEqual(false);
+  });
+
+  it('should validate Date', () => {
+    expect(utils.isDate(new Date())).toEqual(true);
+    expect(utils.isDate(Date.now())).toEqual(false);
+  });
+
+  it('should validate Function', () => {
+    expect(utils.isFunction(function () {})).toEqual(true);
+    expect(utils.isFunction('function')).toEqual(false);
+  });
+
+  it('should validate URLSearchParams', () => {
+    expect(utils.isURLSearchParams(new URLSearchParams())).toEqual(true);
+    expect(utils.isURLSearchParams('foo=1&bar=2')).toEqual(false);
+  });
+
+  it('should validate TypedArray instance', () => {
+    expect(utils.isTypedArray(new Uint8Array([1, 2, 3]))).toEqual(true);
+    expect(utils.isTypedArray([1, 2, 3])).toEqual(false);
+  });
+});

tests/unit/utils/kindOf.test.js

@@ -0,0 +1,13 @@
+import { describe, it, expect } from 'vitest';
+import utils from '../../../lib/utils.js';
+
+const { kindOf } = utils;
+
+describe('utils::kindOf', () => {
+  it('should return object tag', () => {
+    expect(kindOf({})).toEqual('object');
+    // cached result
+    expect(kindOf({})).toEqual('object');
+    expect(kindOf([])).toEqual('array');
+  });
+});

tests/unit/utils/kindOfTest.test.js

@@ -0,0 +1,12 @@
+import { describe, it, expect } from 'vitest';
+import utils from '../../../lib/utils.js';
+
+describe('utils::kindOfTest', () => {
+  it('should return true if the type is matched', () => {
+    const { kindOfTest } = utils;
+    const test = kindOfTest('number');
+
+    expect(test(123)).toEqual(true);
+    expect(test('123')).toEqual(false);
+  });
+});

tests/unit/utils/merge.test.js

@@ -0,0 +1,97 @@
+import { describe, it, expect } from 'vitest';
+import utils from '../../../lib/utils.js';
+
+const { merge } = utils;
+
+describe('utils::merge', () => {
+  it('should be immutable', () => {
+    const a = {};
+    const b = { foo: 123 };
+    const c = { bar: 456 };
+
+    merge(a, b, c);
+
+    expect(typeof a.foo).toEqual('undefined');
+    expect(typeof a.bar).toEqual('undefined');
+    expect(typeof b.bar).toEqual('undefined');
+    expect(typeof c.foo).toEqual('undefined');
+  });
+
+  it('should merge properties', () => {
+    const a = { foo: 123 };
+    const b = { bar: 456 };
+    const c = { foo: 789 };
+    const d = merge(a, b, c);
+
+    expect(d.foo).toEqual(789);
+    expect(d.bar).toEqual(456);
+  });
+
+  it('should merge recursively', () => {
+    const a = { foo: { bar: 123 } };
+    const b = { foo: { baz: 456 }, bar: { qux: 789 } };
+
+    expect(merge(a, b)).toEqual({
+      foo: {
+        bar: 123,
+        baz: 456,
+      },
+      bar: {
+        qux: 789,
+      },
+    });
+  });
+
+  it('should remove all references from nested objects', () => {
+    const a = { foo: { bar: 123 } };
+    const b = {};
+    const d = merge(a, b);
+
+    expect(d).toEqual({
+      foo: {
+        bar: 123,
+      },
+    });
+
+    expect(d.foo).not.toBe(a.foo);
+  });
+
+  it('handles null and undefined arguments', () => {
+    expect(merge(undefined, undefined)).toEqual({});
+    expect(merge(undefined, { foo: 123 })).toEqual({ foo: 123 });
+    expect(merge({ foo: 123 }, undefined)).toEqual({ foo: 123 });
+
+    expect(merge(null, null)).toEqual({});
+    expect(merge(null, { foo: 123 })).toEqual({ foo: 123 });
+    expect(merge({ foo: 123 }, null)).toEqual({ foo: 123 });
+  });
+
+  it('should replace properties with null', () => {
+    expect(merge({}, { a: null })).toEqual({ a: null });
+    expect(merge({ a: null }, {})).toEqual({ a: null });
+  });
+
+  it('should replace properties with arrays', () => {
+    expect(merge({}, { a: [1, 2, 3] })).toEqual({ a: [1, 2, 3] });
+    expect(merge({ a: 2 }, { a: [1, 2, 3] })).toEqual({ a: [1, 2, 3] });
+    expect(merge({ a: { b: 2 } }, { a: [1, 2, 3] })).toEqual({ a: [1, 2, 3] });
+  });
+
+  it('should replace properties with cloned arrays', () => {
+    const a = [1, 2, 3];
+    const d = merge({}, { a });
+
+    expect(d).toEqual({ a: [1, 2, 3] });
+    expect(d.a).not.toBe(a);
+  });
+
+  it('should support caseless option', () => {
+    const a = { x: 1 };
+    const b = { X: 2 };
+    const merged = merge.call({ caseless: true }, a, b);
+
+    expect(merged).toEqual({
+      x: 2,
+    });
+  });
+});

tests/unit/utils/toArray.test.js

@@ -0,0 +1,13 @@
+import { describe, it, expect } from 'vitest';
+import utils from '../../../lib/utils.js';
+
+const { toArray } = utils;
+
+describe('utils::toArray', () => {
+  it('should return null or an array copy depending on input', () => {
+    expect(toArray()).toEqual(null);
+    expect(toArray([])).toEqual([]);
+    expect(toArray([1])).toEqual([1]);
+    expect(toArray([1, 2, 3])).toEqual([1, 2, 3]);
+  });
+});

tests/unit/utils/toFlatObject.test.js

@@ -0,0 +1,13 @@
+import { describe, it, expect } from 'vitest';
+import utils from '../../../lib/utils.js';
+
+const { toFlatObject } = utils;
+
+describe('utils::toFlatObject', () => {
+  it('should resolve object proto chain to a flat object representation', () => {
+    const a = { x: 1 };
+    const b = Object.create(a, { y: { value: 2 } });
+    const c = Object.create(b, { z: { value: 3 } });
+    expect(toFlatObject(c)).toEqual({ x: 1, y: 2, z: 3 });
+  });
+});

tests/unit/utils/trim.test.js

@@ -0,0 +1,12 @@
+import { describe, it, expect } from 'vitest';
+import utils from '../../../lib/utils.js';
+
+describe('utils::trim', () => {
+  it('should trim spaces', () => {
+    expect(utils.trim('  foo  ')).toEqual('foo');
+  });
+
+  it('should trim tabs', () => {
+    expect(utils.trim('\tfoo\t')).toEqual('foo');
+  });
+});

vitest.config.js

@@ -25,6 +25,22 @@ export default defineConfig({
           setupFiles: ['tests/setup/browser.setup.js'],
         },
       },
+      {
+        test: {
+          name: 'browser-headless',
+          include: ['tests/browser/**/*.browser.test.js'],
+          browser: {
+            enabled: true,
+            provider: playwright(),
+            instances: [
+              { browser: 'chromium', headless: true },
+              { browser: 'firefox', headless: true },
+              { browser: 'webkit', headless: true },
+            ],
+          },
+          setupFiles: ['tests/setup/browser.setup.js'],
+        },
+      },
     ],
   },
 });