Question

I have a method that performs an asynchronous service call. I call this class by passing in the callback.

public void GetRights(EventHandler<GetRightsCompletedEventArgs> callback)
{
    ServiceClient client = new ServiceClient();
    client.GetRightsCompleted += new EventHandler<GetRightsCompletedEventArgs>(callback);
    client.GetRightsAsync();
}

GetRights(GetRightsCallback);

I m creating tests with MSTest, and I ve mocked the containing class (IGetRightsProxy) in Moq. How can I invoke the callback when this method is called in the test?

GetRightsForCurrentUserCompletedEventArgs results = 
    new GetRightsCompletedEventArgs(
    new object[] { new ObservableCollection<Right>()}, null, false, null);
Mock<IGetRightsProxy> MockIGetRightsProxy = new Mock<GetRightsProxy>();

Answer 1

One way of doing what I want is to extend the class like this:

class MockGetRightsProxy : IGetRightsProxy
{
    public void GetRights(EventHandler<GetRightsCompletedEventArgs> callback)
    {
        // Create some args here
        GetRightsCompletedEventArgs args = new GetRightsCompletedEventArgs(
            new object[] { new ObservableCollection<Right>() }, null, false, null);

        callback(null, args);
    }

}

I was looking for ways to invoke the callback in Moq, but this works, too.

Answer 2

You want to be looking at Moq s Callback() extension on your mock;

Mock<IGetRightsProxy> mock = new Mock<IGetRightsProxy>();
mock.Setup(x => x.GetRights(It.IsAny<EventHandler<GetRightsCompletedEventArgs>>())
  .Callback<EventHandler<GetRightsCompletedEventArgs>>(
    callback => callback(mock.Object, new GetRightsCompletedEventArgs())
  );

When the code under test calls GetRights() on the IGetRightsProxy mock the actual EventHandler<GetRightsCompletedEventArgs> it passes in will subsequently be passed into Moq s Callback() method.

Note: Type inference will work on the generic applied to Callback() but I find in these cases it is a bit more readable to explicitly define the type being passed into the method.

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