pkg/webhook: test ResourceInterpreterCustomization

In this commit, we introduce unit tests for `ValidationAdmission`
webhook for the `ResourceInterpreterCustomization` resource. The
tests include:

- Tests how the webhook responds when decoding the request object fails.
- Tests how the webhook responds when it fails to retrieve list of objects from a namespace.
- Ensures that invalid `ResourceInterpreterCustomization` spec denies the admission.
- Confirms that valid `ResourceInterpreterCustomization` spec are allowed through without errors.

Signed-off-by: Mohamed Awnallah <mohamedmohey2352@gmail.com>

pkg/webhook/resourceinterpretercustomization/validation_test.go

@@ -0,0 +1,195 @@
+/*
+Copyright 2024 The Karmada 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 resourceinterpretercustomization
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"reflect"
+	"strings"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
+
+	configv1alpha1 "github.com/karmada-io/karmada/pkg/apis/config/v1alpha1"
+)
+
+// ResponseType represents the type of admission response.
+type ResponseType string
+
+const (
+	Denied  ResponseType = "Denied"
+	Allowed ResponseType = "Allowed"
+	Errored ResponseType = "Errored"
+)
+
+// TestResponse is used to define expected response in a test case.
+type TestResponse struct {
+	Type    ResponseType
+	Message string
+}
+
+type fakeValidationDecoder struct {
+	err error
+	obj runtime.Object
+}
+
+// Decode mocks the Decode method of admission.Decoder.
+func (f *fakeValidationDecoder) Decode(_ admission.Request, obj runtime.Object) error {
+	if f.err != nil {
+		return f.err
+	}
+	if f.obj != nil {
+		reflect.ValueOf(obj).Elem().Set(reflect.ValueOf(f.obj).Elem())
+	}
+	return nil
+}
+
+// DecodeRaw mocks the DecodeRaw method of admission.Decoder.
+func (f *fakeValidationDecoder) DecodeRaw(_ runtime.RawExtension, obj runtime.Object) error {
+	if f.err != nil {
+		return f.err
+	}
+	if f.obj != nil {
+		reflect.ValueOf(obj).Elem().Set(reflect.ValueOf(f.obj).Elem())
+	}
+	return nil
+}
+
+// fakeClient is a mock implementation of the client.Client interface for testing.
+type fakeClient struct {
+	client.Client
+	listError error
+}
+
+func (f *fakeClient) List(_ context.Context, _ client.ObjectList, _ ...client.ListOption) error {
+	if f.listError != nil {
+		return f.listError
+	}
+	return nil
+}
+
+func TestValidatingAdmission_Handle(t *testing.T) {
+	tests := []struct {
+		name      string
+		decoder   admission.Decoder
+		req       admission.Request
+		want      TestResponse
+		listError error
+	}{
+		{
+			name: "Handle_DecodeError_DeniesAdmission",
+			decoder: &fakeValidationDecoder{
+				err: errors.New("decode error"),
+			},
+			req: admission.Request{},
+			want: TestResponse{
+				Type:    Errored,
+				Message: "decode error",
+			},
+		},
+		{
+			name: "Handle_ListError_InternalError",
+			decoder: &fakeValidationDecoder{
+				obj: &configv1alpha1.ResourceInterpreterCustomization{},
+			},
+			req:       admission.Request{},
+			listError: errors.New("list error"),
+			want: TestResponse{
+				Type:    Errored,
+				Message: "list error",
+			},
+		},
+		{
+			name: "Handle_WrongLuaCustomizationRetentionScript_DeniesAdmission",
+			decoder: &fakeValidationDecoder{
+				obj: &configv1alpha1.ResourceInterpreterCustomization{
+					Spec: configv1alpha1.ResourceInterpreterCustomizationSpec{
+						Customizations: configv1alpha1.CustomizationRules{
+							Retention: &configv1alpha1.LocalValueRetention{LuaScript: `function Retain(desiredObj, observedObj)`},
+						},
+					},
+				},
+			},
+			req: admission.Request{},
+			want: TestResponse{
+				Type:    Denied,
+				Message: "Lua script error: <string> at EOF",
+			},
+		},
+		{
+			name: "Handle_ValidRequest_AllowsAdmission",
+			decoder: &fakeValidationDecoder{
+				obj: &configv1alpha1.ResourceInterpreterCustomization{
+					Spec: configv1alpha1.ResourceInterpreterCustomizationSpec{
+						Target: configv1alpha1.CustomizationTarget{
+							APIVersion: "foo/v1",
+							Kind:       "bar",
+						},
+					},
+				},
+			},
+			req: admission.Request{},
+			want: TestResponse{
+				Type:    Allowed,
+				Message: "",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			v := &ValidatingAdmission{
+				Client:  &fakeClient{listError: tt.listError},
+				Decoder: tt.decoder,
+			}
+			got := v.Handle(context.Background(), tt.req)
+
+			// Extract type and message from the actual response.
+			gotType := extractResponseType(got)
+			gotMessage := extractErrorMessage(got)
+
+			if gotType != tt.want.Type || !strings.Contains(gotMessage, tt.want.Message) {
+				t.Errorf("Handle() = {Type: %v, Message: %v}, want {Type: %v, Message: %v}", gotType, gotMessage, tt.want.Type, tt.want.Message)
+			}
+		})
+	}
+}
+
+// extractResponseType extracts the type of admission response.
+func extractResponseType(resp admission.Response) ResponseType {
+	if resp.Allowed {
+		return Allowed
+	}
+	if resp.Result != nil {
+		if resp.Result.Code == http.StatusBadRequest || resp.Result.Code == http.StatusInternalServerError {
+			return Errored
+		}
+	}
+	return Denied
+}
+
+// extractErrorMessage extracts the error message from a Denied/Errored response.
+func extractErrorMessage(resp admission.Response) string {
+	if !resp.Allowed && resp.Result != nil {
+		return resp.Result.Message
+	}
+	return ""
+}