public async void LoginCommandShouldCallLoginService()
{
var vm = new LoginViewModel();
await vm.LoginCommand.Execute();
LoginServiceMock.Verify(m => m.Login(), Times.Once());
}
public void ShouldLogoutWhenLoginPageNavigatedTo()
{
var vm = new LoginViewModel();
LoginServiceMock.Verify(l => l.Logout(), Times.Once());
}