使用 Prism 处理 ViewModel 时如何验证 EventAggregator 的取消订阅方法被调用答案

【问题标题】：How to verify the EventAggregator's unsubscribe method is called when disposing a ViewModel with Prism使用 Prism 处理 ViewModel 时如何验证 EventAggregator 的取消订阅方法被调用
【发布时间】：2011-10-06 14:10:43
【问题描述】：

我正在努力编写一个测试，以确认我在 EventAggregator 的消息关闭时正确地取消订阅它。谁能指出（简单）答案？！

代码如下：

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：

Moq.MockVerificationException ：以下设置不匹配： 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();
}

【问题讨论】：

标签： wpf prism moq eventaggregator

【解决方案1】：

在这里，我正在验证 Unsubscribe 是否在模拟的 IssuerSelectedEvent 上被调用

[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>());
}

如果您想检查是否将完全相同的令牌传递到 Unsubscribe，那么您将需要 Setup 用于返回您在测试中创建的令牌的 Subscribe 方法。

【讨论】：

【解决方案2】：

你需要告诉你的EventAggregator模拟返回你模拟的IssuerSelectedEvent：

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

【讨论】：

谢谢 - 我之前试过了，得到了System.NotSupportedException : Invalid setup on a non-virtual (overridable in VB) member: x => x.GetEvent<IssuerSelectedEvent>() 当然，我还需要为 IEventAggregator 创建一个模拟，而不是 EventAggregator，这样现在可以工作了

【解决方案3】：

测试需要更改为：

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

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

    vm.Dispose();

    evnt.VerifyAll();
}

【讨论】：