Mark Baker has posted the third part of his series looking at an alternative way to handle mocking in the tests for your PHP application. In this latest part of the series he shows how to modify one of PHPUnit's own mocking examples to use an anonymous class.
I have heard people say that you shouldn’t test abstract classes or traits, only the concrete classes that implement or use them. I don’t follow that approach: unit testing is all about testing in isolation from anything that might affect those tests. Testing a concrete class that implements an abstract one, or uses a trait, means that the abstract class or trait is no longer fully isolated, but is being tested within the scope of the whole of that concrete class. We should still always test concrete classes as well; but we should also test the abstract classes and traits as individual units.
So just how do we test something that cannot be instantiated on its own?
He shares one tactic that some developers use - a class designed only for testing - but suggests that this "pollutes" the codebase. Instead he shows how to replace mocking for traits and abstract classes with an anonymous class that's more "disposable". He also shows how to modify this approach to handle calling protected methods in the class the anonymous class extends.