public void ShouldCallXyzServiceToSendNotification() { // given var xyzServiceMock = new Mock <IXYZService>(); ABCNotification notification = new Filler <ABCNotification>().Create(); ABCNotificationResponse notificationResponse = new Filler <ABCNotificationResponse>().Create(); xyzServiceMock.Setup(broker => broker.SendNotification(notification)) .Returns(notificationResponse); // when var aService = new AService(xyzServiceMock.Object); aService.DoStuffA(notification); // then xyzServiceMock.Verify( broker => broker.SendNotification(notification), Times.Once); }