You might have expected that by the time you reached the end of this book, you'd know everything about test-driven development (TDD). If that was the case, we're sorry that we'll have to disappoint you. It takes a lot of time and practice to master any craft, and TDD is no exception. Go on, apply what you have learned to your projects. Share knowledge with your colleagues. Most importantly, practice, practice, and practice. As with karate, only through continuous practice and repetition can one fully master TDD. We have been using it for a long time, and we still often face new challenges and learn new ways to improve our craftsmanship.