TDD is a development methodology where application code is driven by tests. In TDD, a failing test is written first and then is followed by application code to fix the test. There is no doubt that TDD works really well in practice, and it complements the Agile development process. This is evident from many success stories and a lot of research done throughout the industry. This chapter had intended to get rid of any reservations the reader may have had about the use of TDD and to give a quick win example. In the next chapter, we will start on a broader problem and will see how the solution can be reached using TDD.