diff --git a/pkg/estimator/service/mock_EstimatorClient_test.go b/pkg/estimator/service/mock_EstimatorClient_test.go
new file mode 100644
index 000000000000..7d99365d3eb9
--- /dev/null
+++ b/pkg/estimator/service/mock_EstimatorClient_test.go
@@ -0,0 +1,202 @@
+/*
+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 service
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/api/resource"
+
+	"github.com/karmada-io/karmada/pkg/estimator/pb"
+)
+
+func TestMockEstimatorClientGetUnschedulableReplicas(t *testing.T) {
+	testCases := []struct {
+		name          string
+		request       *pb.UnschedulableReplicasRequest
+		setupMock     func(*MockEstimatorClient)
+		expectedResp  *pb.UnschedulableReplicasResponse
+		expectedError error
+	}{
+		{
+			name: "successful response",
+			request: &pb.UnschedulableReplicasRequest{
+				Cluster: "cluster-1",
+				Resource: pb.ObjectReference{
+					APIVersion: "apps/v1",
+					Kind:       "Deployment",
+					Namespace:  "default",
+					Name:       "nginx",
+				},
+				UnschedulableThreshold: 5 * time.Minute,
+			},
+			setupMock: func(m *MockEstimatorClient) {
+				expectedResp := &pb.UnschedulableReplicasResponse{
+					UnschedulableReplicas: 3,
+				}
+				m.On("GetUnschedulableReplicas", context.Background(),
+					&pb.UnschedulableReplicasRequest{
+						Cluster: "cluster-1",
+						Resource: pb.ObjectReference{
+							APIVersion: "apps/v1",
+							Kind:       "Deployment",
+							Namespace:  "default",
+							Name:       "nginx",
+						},
+						UnschedulableThreshold: 5 * time.Minute,
+					}).Return(expectedResp, nil)
+			},
+			expectedResp: &pb.UnschedulableReplicasResponse{
+				UnschedulableReplicas: 3,
+			},
+			expectedError: nil,
+		},
+		{
+			name: "error response",
+			request: &pb.UnschedulableReplicasRequest{
+				Cluster: "invalid-cluster",
+				Resource: pb.ObjectReference{
+					APIVersion: "apps/v1",
+					Kind:       "Deployment",
+					Namespace:  "default",
+					Name:       "nginx",
+				},
+			},
+			setupMock: func(m *MockEstimatorClient) {
+				m.On("GetUnschedulableReplicas", context.Background(),
+					&pb.UnschedulableReplicasRequest{
+						Cluster: "invalid-cluster",
+						Resource: pb.ObjectReference{
+							APIVersion: "apps/v1",
+							Kind:       "Deployment",
+							Namespace:  "default",
+							Name:       "nginx",
+						},
+					}).Return(nil, errors.New("cluster not found"))
+			},
+			expectedResp:  nil,
+			expectedError: errors.New("cluster not found"),
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			client := &MockEstimatorClient{}
+			tc.setupMock(client)
+
+			resp, err := client.GetUnschedulableReplicas(context.Background(), tc.request)
+
+			assert.Equal(t, tc.expectedResp, resp)
+			if tc.expectedError != nil {
+				assert.EqualError(t, err, tc.expectedError.Error())
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}
+
+func TestMockEstimatorClientMaxAvailableReplicas(t *testing.T) {
+	testCases := []struct {
+		name          string
+		request       *pb.MaxAvailableReplicasRequest
+		setupMock     func(*MockEstimatorClient)
+		expectedResp  *pb.MaxAvailableReplicasResponse
+		expectedError error
+	}{
+		{
+			name: "successful response",
+			request: &pb.MaxAvailableReplicasRequest{
+				Cluster: "cluster-1",
+				ReplicaRequirements: pb.ReplicaRequirements{
+					NodeClaim: &pb.NodeClaim{
+						NodeSelector: map[string]string{
+							"zone": "us-east-1",
+						},
+						Tolerations: []corev1.Toleration{
+							{
+								Key:      "key1",
+								Operator: corev1.TolerationOpEqual,
+								Value:    "value1",
+								Effect:   corev1.TaintEffectNoSchedule,
+							},
+						},
+					},
+					ResourceRequest: corev1.ResourceList{
+						corev1.ResourceCPU:    resource.MustParse("100m"),
+						corev1.ResourceMemory: resource.MustParse("100Mi"),
+					},
+					Namespace:         "default",
+					PriorityClassName: "high-priority",
+				},
+			},
+			setupMock: func(m *MockEstimatorClient) {
+				expectedResp := &pb.MaxAvailableReplicasResponse{
+					MaxReplicas: 10,
+				}
+				m.On("MaxAvailableReplicas", context.Background(),
+					mock.MatchedBy(func(req *pb.MaxAvailableReplicasRequest) bool {
+						return req.Cluster == "cluster-1" &&
+							req.ReplicaRequirements.Namespace == "default"
+					})).Return(expectedResp, nil)
+			},
+			expectedResp: &pb.MaxAvailableReplicasResponse{
+				MaxReplicas: 10,
+			},
+			expectedError: nil,
+		},
+		{
+			name: "error response",
+			request: &pb.MaxAvailableReplicasRequest{
+				Cluster: "invalid-cluster",
+				ReplicaRequirements: pb.ReplicaRequirements{
+					Namespace: "default",
+				},
+			},
+			setupMock: func(m *MockEstimatorClient) {
+				m.On("MaxAvailableReplicas", context.Background(),
+					mock.MatchedBy(func(req *pb.MaxAvailableReplicasRequest) bool {
+						return req.Cluster == "invalid-cluster"
+					})).Return(nil, errors.New("cluster not found"))
+			},
+			expectedResp:  nil,
+			expectedError: errors.New("cluster not found"),
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			client := &MockEstimatorClient{}
+			tc.setupMock(client)
+
+			resp, err := client.MaxAvailableReplicas(context.Background(), tc.request)
+
+			assert.Equal(t, tc.expectedResp, resp)
+			if tc.expectedError != nil {
+				assert.EqualError(t, err, tc.expectedError.Error())
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}