Another example on ways to to make your code testable

Before you go crazy on me screaming that making code testable for the sake of testability is bad I'd like to agree. However testable code have other nice properties like loose coupling for example - something you likely want. Anyway, in this article there is a great comparison between using inheritance vs composition to implement a class and how that affects both the design of the class and the tests. TL/DR; use composition and dependency injection. Please.