Mocks are not Stubs

As many before me I was recently looking at different mocking frameworks in order to find one that suited my needs, and was written in C++. And there are not many alternatives out there if you're using C++. I've found one open source and two internal (Microsoft staff can access what can be described as an internal codeplex) ones. Pretty soon it turned out that none of these frameworks did what I wanted. Actually they suggested using no framework at all for the situations I was looking to "solve" with a framework.

At this point I rediscovered an old article by Martin Fowler and it became crystal clear that the reason I didn't find what I wanted in the mocking frameworks was because I really wanted a stub framework (or rather a stub helper). Because what I wanted was a simple way to reuse the algorithm "return 17 the first 7 times called and then throw an exception after that, unless called with argument 4711 in which case you should always return 42". A pretty simple method to write in your stub if you just subclass and override the object you want to mock/stub but a little bit cumbersome in the long run if you do this a lot.

During a discussion on a company internal mailing list for TDD it became clear that people generally use the term mock object for almost every kind of non-production object used during testing. And when another large group do make the distinction between mocks, stubs, fakes and dummies you quickly run into trouble since you are no longer discussing the same thing. So here is yet another recap on what the different kinds of objects are so I can contribute to the cause, making world a better place to be. At least when talking about mocks & friends.