c# - 测试订阅 EventAggregator

Question

多亏了这个SO answer我已经成功地测试了 PRISM EventAggregator 的发布事件(用 FakeItEasy 伪装)

[TestCase]
public void test_that_publish_occured()
{
    var fakeEventAg = A.Fake<IEventAggregator>();
    var fakeEvent = A.Fake<MyEvent>();

    A.CallTo(() => fakeEventAg.GetEvent<MyEvent>())
      .Returns(fakeEvent);

    MyViewModel mvm = new MyViewModel(fakeEventAg);

    mvm.ICommandThatCausesPublishToBeCalled.Execute();

    A.CallTo(() => fakeEvent.Publish(A<SomeClass>.Ignored))
      .MustHaveHappened();
}

但是我没有测试订阅这个事件。我尝试了以下方法，但出现异常“无法拦截非虚拟方法”。

[TestCase]
public void test_that_event_is_listened()
{
    var fakeEventAg = A.Fake<IEventAggregator>();
    var fakeEvent = A.Fake<MyEvent>();
    A.CallTo(() => fakeEventAg.GetEvent<MyEvent>())
      .Returns(fakeEvent);

    // subscription occurs in the constructor
    MyViewModel2 mvm2 = new MyViewModel2(fakeEventAg);

    A.CallTo(() => fakeEventAg.GetEvent<MyEvent>()
      .Subscribe(A<Action<PayloadClass>>.Ignored))
      .MustHaveHappened();
}

如何测试事件订阅是否已发生？不一定是单元测试，也可以是集成测试。

Answer 1

错误发生是因为 Subscribe 方法不是虚拟的，因此不能被模拟。我看到 EventBase 类(MyEvent 所基于的)有一个 Subscriptions 属性。您应该能够检查该集合以验证您的事件是否已添加。