I have read its documents, and it is really an interesting test
framework, although I doubt that it is using too many tricky AST
transformations. I think we can get inspiration from it on many aspects,
e.g. AST transformation and especially mocking. And I think you might
want to have a look at its syntax of mocking (it is called 'interaction'
in spock): http://code.google.com/p/spock/wiki/Interactions