Mocking GWT Asynchronous Services with jMock
If you're using GWT you might, as I do, find using GWTTestCase to be too slow for comfort. Instead, you can use JUnit and jMock to test objects that call asynchronous GWT services. The tests run much faster and are, I think, easier to read.
This article on the jMock website explains how: Mocking GWT Asynchronous Services.