Mocking Multiple Return Values with Rhino Mocks

It’s been a while since I’ve found the need to write unit tests using any kind of mocking framework. It always feels a little like cheating to me, like the design is better broken down into smaller chunks and I’m really just ignoring something my code is trying to tell me. That was until my current project really needed it to allow a complicated piece of coordinating glue code to be tested to make sure it was coordinating the right things in the right order.

Having used Rhino Mocks before I fell naturally into using the

MockRepository.GenerateMock<IMyInterface>() 

syntax.

Everything was going nicely until I found I needed to do a bit of conditional logic where the first call to a method needed to return false (stuff is not setup, so please do the work for me) and the next call needed to return true (the pre-work is done, move on to the next stage). I thought this might mean a nasty bit of involved logic but I was surprised to find Rhino gives you this Repeat control relatively easily.

var mockRepo = MockRepository.GenerateMock<IMyMultiStageInterface>();

mockRepo.Expect(r => r.WorkHasBeenDone()).Return(false).Repeat.Once();
mockRepo.Expect(r => r.WorkHasBeenDone()).Return(true);