add integration test to check that Service internalTrafficPolicy is no longer defaulting when Type is ExternalName

Signed-off-by: Andrew Sy Kim <kim.andrewsy@gmail.com>

test/integration/service/service_test.go

@@ -0,0 +1,75 @@
+/*
+Copyright 2022 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 service
+
+import (
+	"context"
+	"testing"
+
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	clientset "k8s.io/client-go/kubernetes"
+	restclient "k8s.io/client-go/rest"
+	"k8s.io/kubernetes/test/integration/framework"
+)
+
+// Test_ExternalNameServiceStopsDefaultingInternalTrafficPolicy tests that Services no longer default
+// the internalTrafficPolicy field when Type is ExternalName. This test exists due to historic reasons where
+// the internalTrafficPolicy field was being defaulted in older versions. New versions stop defauting the
+// field and drop on read, but for compatibility reasons we still accept the field.
+func Test_ExternalNameServiceStopsDefaultingInternalTrafficPolicy(t *testing.T) {
+	controlPlaneConfig := framework.NewIntegrationTestControlPlaneConfig()
+	_, server, closeFn := framework.RunAnAPIServer(controlPlaneConfig)
+	defer closeFn()
+
+	config := restclient.Config{Host: server.URL}
+	client, err := clientset.NewForConfig(&config)
+	if err != nil {
+		t.Fatalf("Error creating clientset: %v", err)
+	}
+
+	ns := framework.CreateTestingNamespace("test-external-name-drops-internal-traffic-policy", server, t)
+	defer framework.DeleteTestingNamespace(ns, server, t)
+
+	service := &corev1.Service{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "test-123",
+		},
+		Spec: corev1.ServiceSpec{
+			Type:         corev1.ServiceTypeExternalName,
+			ExternalName: "foo.bar.com",
+		},
+	}
+
+	service, err = client.CoreV1().Services(ns.Name).Create(context.TODO(), service, metav1.CreateOptions{})
+	if err != nil {
+		t.Fatalf("Error creating test service: %v", err)
+	}
+
+	if service.Spec.InternalTrafficPolicy != nil {
+		t.Errorf("service internalTrafficPolicy should be droppped but is set: %v", service.Spec.InternalTrafficPolicy)
+	}
+
+	service, err = client.CoreV1().Services(ns.Name).Get(context.TODO(), service.Name, metav1.GetOptions{})
+	if err != nil {
+		t.Fatalf("error getting service: %v", err)
+	}
+
+	if service.Spec.InternalTrafficPolicy != nil {
+		t.Errorf("service internalTrafficPolicy should be droppped but is set: %v", service.Spec.InternalTrafficPolicy)
+	}
+}