diff --git a/service/wechat/mock_wechatMessageManager.go b/service/wechat/mock_wechatMessageManager.go
new file mode 100644
index 0000000..975964d
--- /dev/null
+++ b/service/wechat/mock_wechatMessageManager.go
@@ -0,0 +1,27 @@
+// Code generated by mockery 2.7.4. DO NOT EDIT.
+
+package wechat
+
+import (
+	message "github.com/silenceper/wechat/v2/officialaccount/message"
+	mock "github.com/stretchr/testify/mock"
+)
+
+// mockWechatMessageManager is an autogenerated mock type for the wechatMessageManager type
+type mockWechatMessageManager struct {
+	mock.Mock
+}
+
+// Send provides a mock function with given fields: msg
+func (_m *mockWechatMessageManager) Send(msg *message.CustomerMessage) error {
+	ret := _m.Called(msg)
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func(*message.CustomerMessage) error); ok {
+		r0 = rf(msg)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
diff --git a/service/wechat/wechat.go b/service/wechat/wechat.go
index 383c6b3..46638c7 100644
--- a/service/wechat/wechat.go
+++ b/service/wechat/wechat.go
@@ -23,10 +23,15 @@ type Config struct {
     EncodingAESKey 	string
 }
 
+// wechatMessageManager abstracts go-wechat's message.Manager for writing unit tests
+type wechatMessageManager interface {
+    Send(msg *message.CustomerMessage) error
+}
+
 // Service encapsulates the WeChat client along with internal state for storing users.
 type Service struct {
     config 			Config
-    messageManager	*message.Manager
+    messageManager	wechatMessageManager
     userIDs 		[]string
 }
 
diff --git a/service/wechat/wechat_test.go b/service/wechat/wechat_test.go
new file mode 100644
index 0000000..6ecbd52
--- /dev/null
+++ b/service/wechat/wechat_test.go
@@ -0,0 +1,52 @@
+package wechat
+
+import (
+    "context"
+    "github.com/silenceper/wechat/v2/officialaccount/message"
+    "github.com/pkg/errors"
+    "github.com/stretchr/testify/require"
+	"testing"
+)
+
+func TestAddReceivers(t *testing.T) {
+	assert := require.New(t)
+
+	svc := &Service{
+		userIDs: []string{},
+	}
+	userIDs := []string{"User1ID", "User2ID", "User3ID"}
+	svc.AddReceivers(userIDs...)
+
+	assert.Equal(svc.userIDs, userIDs)
+}
+
+func TestSend(t *testing.T) {
+	assert := require.New(t)
+
+	svc := &Service{
+        userIDs: []string{},
+	}
+
+	// test wechat message manager returning error
+	mockMsgManager := new(mockWechatMessageManager)
+    mockMsgManager.On("Send", message.NewCustomerTextMessage("UserID1", "subject\nmessage")).
+	    Return(errors.New("some error"))
+    svc.messageManager = mockMsgManager
+	svc.AddReceivers("UserID1")
+	ctx := context.Background()
+	err := svc.Send(ctx, "subject", "message")
+	assert.NotNil(err)
+    mockMsgManager.AssertExpectations(t)
+
+	// test success and multiple receivers
+    mockMsgManager = new(mockWechatMessageManager)
+    mockMsgManager.On("Send", message.NewCustomerTextMessage("UserID1", "subject\nmessage")).
+        Return(nil)
+    mockMsgManager.On("Send", message.NewCustomerTextMessage("UserID2", "subject\nmessage")).
+        Return(nil)
+	svc.messageManager = mockMsgManager
+	svc.AddReceivers("UserID1", "UserID2")
+	err = svc.Send(ctx, "subject", "message")
+	assert.Nil(err)
+    mockMsgManager.AssertExpectations(t)
+}