test: Add integration test for apiserver statusz endpoint

test/integration/controlplane/kube_apiserver_test.go

@@ -160,6 +160,36 @@ Warning: This endpoint is not meant to be machine parseable, has no formatting c
 	}
 }
 
+func TestStatusz(t *testing.T) {
+	featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.ComponentStatusz, true)
+	server := kubeapiservertesting.StartTestServerOrDie(t, nil, framework.DefaultTestServerFlags(), framework.SharedEtcd())
+	defer server.TearDownFn()
+
+	client, err := kubernetes.NewForConfig(server.ClientConfig)
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+
+	res := client.CoreV1().RESTClient().Get().RequestURI("/statusz").Do(context.TODO())
+	var status int
+	res.StatusCode(&status)
+	if status != http.StatusOK {
+		t.Fatalf("statusz/ should be healthy, got %v", status)
+	}
+
+	expectedHeader := `
+kube-apiserver statusz
+Warning: This endpoint is not meant to be machine parseable, has no formatting compatibility guarantees and is for debugging purposes only.`
+
+	raw, err := res.Raw()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.HasPrefix(raw, []byte(expectedHeader)) {
+		t.Fatalf("Header mismatch!\nExpected:\n%s\n\nGot:\n%s", expectedHeader, string(raw))
+	}
+}
+
 // TestOpenAPIDelegationChainPlumbing is a smoke test that checks for
 // the existence of some representative paths from the
 // apiextensions-server and the kube-aggregator server, both part of