diff --git a/render/render_msgpack_test.go b/render/render_msgpack_test.go
index 579897cc..b0eaac1b 100644
--- a/render/render_msgpack_test.go
+++ b/render/render_msgpack_test.go
@@ -8,6 +8,7 @@ package render
 
 import (
 	"bytes"
+	"errors"
 	"net/http/httptest"
 	"testing"
 
@@ -16,9 +17,6 @@ import (
 	"github.com/ugorji/go/codec"
 )
 
-// TODO unit tests
-// test errors
-
 func TestRenderMsgPack(t *testing.T) {
 	w := httptest.NewRecorder()
 	data := map[string]any{
@@ -42,3 +40,43 @@ func TestRenderMsgPack(t *testing.T) {
 	assert.Equal(t, w.Body.String(), buf.String())
 	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"))
+
+	// Verify the encoded data is correct
+	h := new(codec.MsgpackHandle)
+	buf := bytes.NewBuffer([]byte{})
+	err = codec.NewEncoder(buf, h).Encode(data)
+	require.NoError(t, err)
+
+	assert.Equal(t, buf.String(), w.Body.String())
+}
+
+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")
+}