Question

I have a method which doesn’t return a value. It instead accepts a list and modifies the members of this list. Obviously the list itself is mutable, as are its members.

EG: I want to mock this:

    void modifyRequests(List<MutableObject> requests);

Answer 1

Well, various mocking frameworks do provide ways of doing this (executing custom actions which use the parameters when a method is invoked) – but I would strongly consider not using mocking. Unless you really want to validate the protocol between your class-under-test and its collaborators, you should consider writing a fake instead of a mock. Then you can make the fake behave however you like – and typically (IME) you end up with simpler test code.

It’s not always appropriate, and mocking certainly has its place – but over time I’ve found that a well-written fake can be worth its weight in gold, particularly if it’s a dependency used by many classes.