使用Prism放置ViewModel时，将调用如何验证EventAggregator的unsubscribe方法 [英] How to verify the EventAggregator's unsubscribe method is called when disposing a ViewModel with Prism

问题描述

我正在努力编写一个测试，以确认关闭了EventAggregator消息后，我正确地取消了订阅.任何人都可以指出(简单的)答案吗?！

I'm struggling to write a test that confirms that I am correctly unsubscribing from an EventAggregator's message when it is closed. Anyone able to point out the (simple) answer?!

这是代码:

public class ViewModel : BaseViewModel, IViewModel
{
    private readonly IEventAggregator eventAggregator;
    private SubscriptionToken token;
    IssuerSelectedEvent issuerSelectedEvent;

    public ViewModel(IView view, IEventAggregator eventAggregator)
    {
        this.eventAggregator = eventAggregator;
        View = view;        

        issuerSelectedEvent = eventAggregator.GetEvent<IssuerSelectedEvent>();
        token = issuerSelectedEvent.Subscribe(SelectedIssuerChanged, true);            
    }

    private void SelectedIssuerChanged(IssuerSelectedCommand obj)
    {
        Console.WriteLine(obj);
    }

    public IView View { get; set; }

    public override void Dispose()
    {
        issuerSelectedEvent.Unsubscribe(token);
    }
}

测试失败，并显示以下信息:

The test fails with:

Moq.MockVerificationException:以下设置不匹配: IssuerSelectedEvent x => x.Unsubscribe(It.IsAny())

Moq.MockVerificationException : The following setups were not matched: IssuerSelectedEvent x => x.Unsubscribe(It.IsAny())

这是测试:

[Test]
public void UnsubscribeFromEventAggregatorOnDispose()
{            
    var view = new Mock<ICdsView>();
    var ea = new Mock<EventAggregator>();
    var evnt = new Mock<IssuerSelectedEvent>();

    evnt.Setup(x => x.Unsubscribe(It.IsAny<SubscriptionToken>()));

    var vm = new CdsIssuerScreenViewModel(view.Object, ea.Object);

    vm.Dispose();

    evnt.VerifyAll();
}

推荐答案

在这里，我正在验证是否在模拟的IssuerSelectedEvent

Here I am verifying that the Unsubscribe was called on the mocked IssuerSelectedEvent

[Test]
public void UnsubscribeFromEventAggregatorOnDispose()
{            
    var view = new Mock<ICdsView>();
    var ea = new Mock<IEventAggregator>();
    var evnt = new Mock<IssuerSelectedEvent>();

    ea.Setup(x => x.GetEvent<IssuerSelectedEvent>()).Returns(evnt.Object);

    var vm = new CdsIssuerScreenViewModel(view.Object, ea.Object);

    vm.Dispose();

    evnt.Verify(x => x.Unsubscribe(It.IsAny<SubscriptionToken>());
}

如果要检查是否将完全相同的令牌传递到Unsubscribe中，则对于Subscribe方法，您将需要Setup，该方法将返回您在测试中创建的令牌.

If you want to check that the exact same token is passed into the Unsubscribe then you will need a Setup for the Subscribe method that returns a token you create in your test.

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