The beauty of Framework for Integrated Tests (FIT) is that it enables the customer or business side of an organization to get involved in the testing process early (i.e., during development). Whereas JUnit’s strength lies in unit testing during the coding process. This article shows you how to combine the best of FIT and JUnit for better teamwork and effective end-to-end testing.
This looks like it would be good for simple constraint testing. Not sure about more complex stuff — but it’s a very good start.