diff --git a/pkg/estimator/client/service_test.go b/pkg/estimator/client/service_test.go
new file mode 100644
index 000000000000..9d074e7864db
--- /dev/null
+++ b/pkg/estimator/client/service_test.go
@@ -0,0 +1,172 @@
+/*
+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 client
+
+import (
+	"context"
+	"testing"
+
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/util/intstr"
+	"k8s.io/client-go/kubernetes/fake"
+)
+
+func TestResolveCluster(t *testing.T) {
+	tests := []struct {
+		name        string
+		namespace   string
+		id          string
+		port        int32
+		service     *corev1.Service
+		expectError bool
+		expected    string
+	}{
+		{
+			name:      "Service not found",
+			namespace: "default",
+			id:        "nonexistent",
+			port:      80,
+			service:   nil,
+			expected:  "nonexistent.default.svc.cluster.local:80",
+		},
+		{
+			name:      "Unsupported service type",
+			namespace: "default",
+			id:        "myservice",
+			port:      80,
+			service: &corev1.Service{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "myservice",
+					Namespace: "default",
+				},
+				Spec: corev1.ServiceSpec{
+					Type: corev1.ServiceTypeClusterIP,
+				},
+			},
+			expectError: true,
+		},
+		{
+			name:      "ExternalName service with int target port",
+			namespace: "default",
+			id:        "myservice",
+			port:      80,
+			service: &corev1.Service{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "myservice",
+					Namespace: "default",
+				},
+				Spec: corev1.ServiceSpec{
+					Type:         corev1.ServiceTypeExternalName,
+					ExternalName: "example.com",
+					Ports: []corev1.ServicePort{
+						{
+							Port:       80,
+							TargetPort: intstr.FromInt(8080),
+						},
+					},
+				},
+			},
+			expected: "example.com:8080",
+		},
+		{
+			name:      "ExternalName service with non-int target port",
+			namespace: "default",
+			id:        "myservice",
+			port:      80,
+			service: &corev1.Service{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "myservice",
+					Namespace: "default",
+				},
+				Spec: corev1.ServiceSpec{
+					Type:         corev1.ServiceTypeExternalName,
+					ExternalName: "example.com",
+					Ports: []corev1.ServicePort{
+						{
+							Port:       80,
+							TargetPort: intstr.FromString("http"),
+						},
+					},
+				},
+			},
+			expectError: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			clientset := fake.NewSimpleClientset()
+			if tt.service != nil {
+				_, err := clientset.CoreV1().Services(tt.namespace).Create(context.TODO(), tt.service, metav1.CreateOptions{})
+				if err != nil {
+					t.Fatalf("failed to create service: %v", err)
+				}
+			}
+
+			result, err := resolveCluster(clientset, tt.namespace, tt.id, tt.port)
+			if (err != nil) != tt.expectError {
+				t.Errorf("expected error: %v, got: %v", tt.expectError, err)
+			}
+			if result != tt.expected {
+				t.Errorf("expected: %s, got: %s", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestFindServicePort(t *testing.T) {
+	tests := []struct {
+		name        string
+		service     *corev1.Service
+		port        int32
+		expectError bool
+	}{
+		{
+			name: "Port found",
+			service: &corev1.Service{
+				Spec: corev1.ServiceSpec{
+					Ports: []corev1.ServicePort{
+						{Port: 80},
+					},
+				},
+			},
+			port: 80,
+		},
+		{
+			name: "Port not found",
+			service: &corev1.Service{
+				Spec: corev1.ServiceSpec{
+					Ports: []corev1.ServicePort{
+						{Port: 8080},
+					},
+				},
+			},
+			port:        80,
+			expectError: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := findServicePort(tt.service, tt.port)
+			if (err != nil) != tt.expectError {
+				t.Errorf("expected error: %v, got: %v", tt.expectError, err)
+			}
+		})
+	}
+}