In my last blog post I discussed what makes unit tests valuable and how to structure your code so that you can write valuable unit tests. But so far I haven’t got into the nitty gritty of how you should write these valuable unit tests. I’ll address that in this blog post. There are three styles of unit test: Output Verification , also known as the functional style, involves checking the output of a method for a given input. This style of unit testing does not concern itself with the internals of a method. State Verification involves checking the state of an object rather than the output of a method. Collaboration Verification is where collaboration between classes is tested, and it usually involves test doubles such as mocks. See Vladimir Khorikov’s blog post for further information and code examples: http://enterprisecraftsmanship.com/2016/06/09/styles-of-unit-testing/ So which style is best for writing valuable unit tests? Here are the four attributes of a v