public async Task Logout() { //Setup var sessionMock = new Mock <ISessionService>(); var eventAggMock = new Mock <IEventAggregator>(); var clientMock = new Mock <IApiClient>(); var model = new ServerListViewModel(sessionMock.Object, eventAggMock.Object, clientMock.Object); //Act model.Servers = new BindableCollection <Server>(); model.Logout(); //Assert sessionMock.Verify(m => m.Logout(), Times.Once); Assert.IsNull(model.Servers); }