core/v1: add validation and defaulting unit tests for when internalTrafficPolicy is nil and Service type is ExternalName

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

pkg/apis/core/validation/validation_test.go

@@ -12281,6 +12281,16 @@ func TestValidateServiceCreate(t *testing.T) {
 			featureGates: []featuregate.Feature{features.ServiceInternalTrafficPolicy},
 			numErrs:      1,
 		},
+		{
+			name: "internalTrafficPolicy field nil when type is ExternalName",
+			tweakSvc: func(s *core.Service) {
+				s.Spec.InternalTrafficPolicy = nil
+				s.Spec.Type = core.ServiceTypeExternalName
+				s.Spec.ExternalName = "foo.bar.com"
+			},
+			featureGates: []featuregate.Feature{features.ServiceInternalTrafficPolicy},
+			numErrs:      0,
+		},
 		{
 			name: "invalid internalTraffic field",
 			tweakSvc: func(s *core.Service) {