test(render): add comprehensive tests for MsgPack render (#4537)

* test(render): add comprehensive tests for MsgPack render

* test(render): make msgpack tests deterministic

Decode the rendered msgpack output and assert values instead of comparing raw bytes (which can vary with map iteration order).
Enable MsgpackHandle.RawToString so msgpack strings decode as Go strings.

---------

Co-authored-by: AmirHossein Fallah <amirhossein.fallah@arvancloud.ir>

render/render_msgpack_test.go

@@ -7,7 +7,7 @@
 package render
 
 import (
-	"bytes"
+	"errors"
 	"net/http/httptest"
 	"testing"
 
@@ -16,9 +16,6 @@ import (
 	"github.com/ugorji/go/codec"
 )
 
-// TODO unit tests
-// test errors
-
 func TestRenderMsgPack(t *testing.T) {
 	w := httptest.NewRecorder()
 	data := map[string]any{
@@ -32,13 +29,52 @@ func TestRenderMsgPack(t *testing.T) {
 
 	require.NoError(t, err)
 
-	h := new(codec.MsgpackHandle)
-	assert.NotNil(t, h)
-	buf := bytes.NewBuffer([]byte{})
-	assert.NotNil(t, buf)
-	err = codec.NewEncoder(buf, h).Encode(data)
-
+	var decoded map[string]any
+	var mh codec.MsgpackHandle
+	mh.RawToString = true
+	err = codec.NewDecoderBytes(w.Body.Bytes(), &mh).Decode(&decoded)
 	require.NoError(t, err)
-	assert.Equal(t, w.Body.String(), buf.String())
+	assert.Equal(t, data, decoded)
 	assert.Equal(t, "application/msgpack; charset=utf-8", w.Header().Get("Content-Type"))
 }
+
+func TestWriteMsgPack(t *testing.T) {
+	w := httptest.NewRecorder()
+	data := map[string]any{
+		"foo": "bar",
+		"num": 42,
+	}
+
+	err := WriteMsgPack(w, data)
+	require.NoError(t, err)
+
+	assert.Equal(t, "application/msgpack; charset=utf-8", w.Header().Get("Content-Type"))
+
+	var decoded map[string]any
+	var mh codec.MsgpackHandle
+	mh.RawToString = true
+	err = codec.NewDecoderBytes(w.Body.Bytes(), &mh).Decode(&decoded)
+	require.NoError(t, err)
+	assert.Len(t, decoded, 2)
+	assert.Equal(t, "bar", decoded["foo"])
+	assert.EqualValues(t, 42, decoded["num"])
+}
+
+type failWriter struct {
+	*httptest.ResponseRecorder
+}
+
+func (w *failWriter) Write(data []byte) (int, error) {
+	return 0, errors.New("write error")
+}
+
+func TestRenderMsgPackError(t *testing.T) {
+	w := httptest.NewRecorder()
+	data := map[string]any{
+		"foo": "bar",
+	}
+
+	err := (MsgPack{data}).Render(&failWriter{w})
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "write error")
+}