add test for inmemory response writer

staging/src/k8s.io/apiserver/pkg/util/responsewriter/inmemoryresponsewriter_test.go

@@ -0,0 +1,63 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package responsewriter
+
+import (
+	"net/http"
+	"testing"
+)
+
+func TestInMemoryResponseWriter(t *testing.T) {
+	w := NewInMemoryResponseWriter()
+
+	h := w.Header()
+	h.Set("Content-Type", "application/json")
+
+	w.WriteHeader(http.StatusCreated)
+
+	_, err := w.Write([]byte(`{"message": "hello"}`))
+	if err != nil {
+		t.Errorf("Write() returned an error: %v", err)
+	}
+
+	if w.RespCode() != http.StatusCreated {
+		t.Errorf("RespCode() returned unexpected code: %d, want %d", w.RespCode(), http.StatusCreated)
+	}
+
+	if string(w.Data()) != `{"message": "hello"}` {
+		t.Errorf("Data() returned unexpected body: %s, want %s", string(w.Data()), `{"message": "hello"}`)
+	}
+
+	expectedString := "ResponseCode: 201, Body: {\"message\": \"hello\"}, Header: map[Content-Type:[application/json]]"
+	if w.String() != expectedString {
+		t.Errorf("String() returned unexpected output: %s, want %s", w.String(), expectedString)
+	}
+}
+
+func TestInMemoryResponseWriter_DefaultHeader(t *testing.T) {
+	w := NewInMemoryResponseWriter()
+
+	_, err := w.Write([]byte(`{"message": "hello"}`))
+	if err != nil {
+		t.Errorf("Write() returned an error: %v", err)
+	}
+
+	// should be StatusOK (200) by default
+	if w.RespCode() != http.StatusOK {
+		t.Errorf("RespCode() returned unexpected code: %d, want %d", w.RespCode(), http.StatusOK)
+	}
+}