그냥 컴퓨터에게 물어보기

코드가 잘 돌아갈지 머리 속으로 고민하지 말고 그냥 단위 테스트를 돌려보기:

Rather than apply minutes of suspect reasoning, we can just ask the computer by making the change and running the tests. In teaching TDD, I see this situation all the time—excellent software engineers spending 5 to 10 minutes reasoning about a question that the computer could answer in 15 seconds. Without the tests you have no choice, you have to reason. With the tests you can decide whether an experiment would answer the question faster. Sometimes you should just ask the computer. —Chapter 10, Test-driven development: by example