The Inviqa techPortal has a new post today from Marcello Duarte about using Prophecy in unit testing to work with mocks and doubles.
Test doubles are a way of replacing all classes in our tests other than the one we are testing. They give us control on direct and indirect outputs that would have been generated by those classes. Understanding the role of the test double helps us to write better tests, and thus better code. [...] When writing unit tests we are focusing on describing one unit of behaviour at a time, and how objects communicate in order to achieve that behaviour. We instantiate the object under test, call a method of the object and observe if the outcome is as expected.
In his examples he uses Prophecy to mock out different kinds of objects - a dummy object, a "fake" (with listeners for other object calls), a stub that mocks other internal method calls and a more familiar mock object. He also talks about two guidelines to follow when thinking about writing tests and code complexity - the Law of Demeter and "Don't Mock What You Don't Own." He gives an example of working around this last one by using the Adapter design pattern.