How do I test Prism event aggregator subscriptions, on the UIThread?

Question

I have a class, that subscribes to an event via PRISMs event aggregator.

As it is somewhat hard to mock the event aggregator as noted here, I just instantiate a real

Answer 1

If you mock both the event and the Event Aggregator, and use moq's Callback, you can do it.

Here's an example:

Mock mockEventAggregator;
Mock mockEvent;

mockEventAggregator.Setup(e => e.GetEvent()).Returns(mockEvent.Object);

// Get a copy of the callback so we can "Publish" the data
Action callback = null;

mockEvent.Setup(
    p =>
    p.Subscribe(
        It.IsAny>(), 
        It.IsAny(), 
        It.IsAny(), 
        It.IsAny>()))
        .Callback, ThreadOption, bool, Predicate>(
        (e, t, b, a) => callback = e);


// Do what you need to do to get it to subscribe

// Callback should now contain the callback to your event handler
// Which will allow you to invoke the callback on the test's thread
// instead of the UI thread
callback.Invoke(new MyEventArgs(someObject));

// Assert