I have some very test-unfriendly code (to say the least) that I need to test. Refactoring unfortunately is not an option. I have to test the code as it is, without the possibility of changing it. To do that, I was thinking of intercepting function calls and dynamically change what they do so I can run my tests, as I need some functions and methods to return known values, and I need others that make requests, connect to the database, etc, to stop doing that and return what I need them to return. Is there any way to do this without runkit_method_redefine(), which is preferably not "EXPERIMENTAL" and still maintained? Maybe an alternative to runkit? Maybe a better way? Edit: will use PHPUnit's test doubles and PHP 5.3.2's features for making private methods accessible, if I need that functionality.