c# - Verifying event registration using Moq

Question

I'm developing an asp.net (classic) application trying to implement the MVP pattern using this example. In trying to unit test my presenter and using the following pattern, the psuedocode for which looks like so

//base view interface
public interface IView
{
    event EventHandler Init;

    event EventHandler Load;

    bool IsPostBack { get; }

    void DataBind();

    bool IsValid { get;}
}

//presenter psuedo code
public class SomePresenter
{
     public SomePresenter(ISomeDomainService service, IView someView)
     {
           ...
           //HOW DO WE TEST/VERIFY THAT THIS REGISTRATION OCCURS?
           someView.Init += OnInit;
           someView.Load += OnLoad;
     }
}
...
//consuming code that exercises the above code, that needs to be tested
var presenter = new SomePresenter(someDomainService, someView);

How do I verify that the presenter is doing what is expected i.e. registering for the Init and Load events? While this is easily done in the Phil Haack's example using Rhino mocks...

[Test]
public void VerifyAttachesToViewEvents()
{
    viewMock.Load += null;
    LastCall.IgnoreArguments();
    viewMock.PostSaved += null;
    LastCall.IgnoreArguments();
    mocks.ReplayAll();
    new PostEditController(viewMock, 
      this.dataServiceMock);
    mocks.VerifyAll();
}

... how can we do this using MOQ?

Answer 1

The moq 4.13 introduced this feature. Now it is possible to verify if add emove has been invoked. Therefore four new methods have been introduced:

1. SetupAdd
2. SetupRemove
3. VerifyAdd
4. VerifyRemove

Example

var mock = new Mock<IAdder<EventArgs>>();
mock.SetupAdd(m => m.Added += (sender, args) => { });

mock.Object.Added += (sender, args) => { };
mock.Object.Added += (sender, args) => { };

mock.VerifyAdd(m => m.Added += It.IsAny<EventHandler>(), Times.Exactly(2));

---

NB: Notice that in order to verify at least one setup should be added. The reason is to keep backward compatibility with the older version of moq.