At this time, we know how TDD works: writing tests before, implementation after tests, and refactoring later on. We are going to pass through that process and only show the final result for each requirement. It is left to you to figure out the iterative red-green-refactor process. Let's make this more interesting, if possible, by using a Hamcrest framework in our tests.
As described in Chapter 2, Tools, Frameworks, and Environment, Hamcrest improves our tests readability. It turns assertions more semantic and comprehensive at the time that complexity is reduced by using matchers. When a test fails, the error shown becomes more expressive by interpreting the matchers used in the assertion. A message could also be added by the developer.
The Hamcrest library is full of different matchers for different object types and collections. Let's start coding and get a taste of it.