public void SendMessage_Calls_ModelSendMessage() { const string userName = "******"; const string message = "test message"; var mainModelMock = new Mock<IMainChatModel>(); mainModelMock.SetupGet(x => x.UserName).Returns(userName); var mainViewModel = new MainPageViewModel(mainModelMock.Object); var chatModelMock = new Mock<IChatModel>(); var viewModel = new PersonalChatViewModel(chatModelMock.Object, mainViewModel); viewModel.SendMessage(message); chatModelMock.Verify(x => x.SendMessage(userName, message), Times.Exactly(1), "Model method 'SendMessage' wasn't called."); }