"Great books begin with great openings. 'Test-Driven Development' by Kent Beck (2003) begins with this sentence: Clean code that works, in Ron Jeffries' pithy phrase, is the goal of Test-Driven Development (TDD)." (Quoted from talks by Takuto Wada (和田卓人), or t_wada, the TDD evangelist actively working in Japan.) When I teach about TDD, I always try to stress that TDD is just a skill and that's Cle