ReplicationController: Add declarative validation test suite

Introduce a test suite that ensures declarative test cases
are fully tested and that validation errors are compared
with handwritten validation to ensure consistency.

Co-authored-by: Tim Hockin <thockin@google.com>
Co-authored-by: Aaron Prindle <aprindle@google.com>
Co-authored-by: Yongrui Lin <yongrlin@google.com>

pkg/registry/core/replicationcontroller/declarative_validation_test.go

@@ -0,0 +1,164 @@
+/*
+Copyright 2025 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 replicationcontroller
+
+import (
+	"testing"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	genericapirequest "k8s.io/apiserver/pkg/endpoints/request"
+	utilfeature "k8s.io/apiserver/pkg/util/feature"
+	featuregatetesting "k8s.io/component-base/featuregate/testing"
+	podtest "k8s.io/kubernetes/pkg/api/pod/testing"
+	apitesting "k8s.io/kubernetes/pkg/api/testing"
+	api "k8s.io/kubernetes/pkg/apis/core"
+	"k8s.io/kubernetes/pkg/features"
+)
+
+func TestDeclarativeValidateForDeclarative(t *testing.T) {
+	ctx := genericapirequest.WithRequestInfo(genericapirequest.NewDefaultContext(), &genericapirequest.RequestInfo{
+		APIGroup:   "",
+		APIVersion: "v1",
+	})
+	testCases := map[string]struct {
+		input        api.ReplicationController
+		expectedErrs field.ErrorList
+	}{
+		"empty resource": {
+			input: mkValidReplicationController(),
+		},
+		// TODO: Add test cases
+	}
+	for k, tc := range testCases {
+		t.Run(k, func(t *testing.T) {
+			var declarativeTakeoverErrs field.ErrorList
+			var imperativeErrs field.ErrorList
+			for _, gateVal := range []bool{true, false} {
+				// We only need to test both gate enabled and disabled together, because
+				// 1) the DeclarativeValidationTakeover won't take effect if DeclarativeValidation is disabled.
+				// 2) the validation output, when only DeclarativeValidation is enabled, is the same as when both gates are disabled.
+				featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.DeclarativeValidation, gateVal)
+				featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.DeclarativeValidationTakeover, gateVal)
+
+				errs := Strategy.Validate(ctx, &tc.input)
+				if gateVal {
+					declarativeTakeoverErrs = errs
+				} else {
+					imperativeErrs = errs
+				}
+				// The errOutputMatcher is used to verify the output matches the expected errors in test cases.
+				errOutputMatcher := field.ErrorMatcher{}.ByType().ByField().ByOrigin()
+				if len(tc.expectedErrs) > 0 {
+					errOutputMatcher.Test(t, tc.expectedErrs, errs)
+				} else if len(errs) != 0 {
+					t.Errorf("expected no errors, but got: %v", errs)
+				}
+			}
+			// The equivalenceMatcher is used to verify the output errors from hand-written imperative validation
+			// are equivalent to the output errors when DeclarativeValidationTakeover is enabled.
+			equivalenceMatcher := field.ErrorMatcher{}.ByType().ByField().ByOrigin()
+			equivalenceMatcher.Test(t, imperativeErrs, declarativeTakeoverErrs)
+
+			apitesting.VerifyVersionedValidationEquivalence(t, &tc.input, nil)
+		})
+	}
+}
+
+func TestValidateUpdateForDeclarative(t *testing.T) {
+	ctx := genericapirequest.WithRequestInfo(genericapirequest.NewDefaultContext(), &genericapirequest.RequestInfo{
+		APIGroup:   "",
+		APIVersion: "v1",
+	})
+	testCases := map[string]struct {
+		old          api.ReplicationController
+		update       api.ReplicationController
+		expectedErrs field.ErrorList
+	}{
+		// TODO: Add test cases
+	}
+	for k, tc := range testCases {
+		t.Run(k, func(t *testing.T) {
+			tc.old.ObjectMeta.ResourceVersion = "1"
+			tc.update.ObjectMeta.ResourceVersion = "1"
+			var declarativeTakeoverErrs field.ErrorList
+			var imperativeErrs field.ErrorList
+			for _, gateVal := range []bool{true, false} {
+				// We only need to test both gate enabled and disabled together, because
+				// 1) the DeclarativeValidationTakeover won't take effect if DeclarativeValidation is disabled.
+				// 2) the validation output, when only DeclarativeValidation is enabled, is the same as when both gates are disabled.
+				featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.DeclarativeValidation, gateVal)
+				featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.DeclarativeValidationTakeover, gateVal)
+				errs := Strategy.ValidateUpdate(ctx, &tc.update, &tc.old)
+				if gateVal {
+					declarativeTakeoverErrs = errs
+				} else {
+					imperativeErrs = errs
+				}
+				// The errOutputMatcher is used to verify the output matches the expected errors in test cases.
+				errOutputMatcher := field.ErrorMatcher{}.ByType().ByField().ByOrigin()
+
+				if len(tc.expectedErrs) > 0 {
+					errOutputMatcher.Test(t, tc.expectedErrs, errs)
+				} else if len(errs) != 0 {
+					t.Errorf("expected no errors, but got: %v", errs)
+				}
+			}
+			// The equivalenceMatcher is used to verify the output errors from hand-written imperative validation
+			// are equivalent to the output errors when DeclarativeValidationTakeover is enabled.
+			equivalenceMatcher := field.ErrorMatcher{}.ByType().ByField().ByOrigin()
+			// TODO: remove this once ErrorMatcher has been extended to handle this form of deduplication.
+			dedupedImperativeErrs := field.ErrorList{}
+			for _, err := range imperativeErrs {
+				found := false
+				for _, existingErr := range dedupedImperativeErrs {
+					if equivalenceMatcher.Matches(existingErr, err) {
+						found = true
+						break
+					}
+				}
+				if !found {
+					dedupedImperativeErrs = append(dedupedImperativeErrs, err)
+				}
+			}
+			equivalenceMatcher.Test(t, dedupedImperativeErrs, declarativeTakeoverErrs)
+
+			apitesting.VerifyVersionedValidationEquivalence(t, &tc.update, &tc.old)
+		})
+	}
+}
+
+// Helper function for RC tests.
+func mkValidReplicationController(tweaks ...func(rc *api.ReplicationController)) api.ReplicationController {
+	rc := api.ReplicationController{
+		ObjectMeta: metav1.ObjectMeta{Name: "abc", Namespace: metav1.NamespaceDefault},
+		Spec: api.ReplicationControllerSpec{
+			Replicas: 1,
+			Selector: map[string]string{"a": "b"},
+			Template: &api.PodTemplateSpec{
+				ObjectMeta: metav1.ObjectMeta{
+					Labels: map[string]string{"a": "b"},
+				},
+				Spec: podtest.MakePodSpec(),
+			},
+		},
+	}
+	for _, tweak := range tweaks {
+		tweak(&rc)
+	}
+	return rc
+}