Today, TDD is rereaded, and individuals think that foreword is the essence of essence. I want to come, if you have a stomach, you only give you half a minute, I believe this half a minute should be the essence you want to say. Relative to XP, TDD should be a technique that can be accepted by more extensive people. And the individual believes that TDD contains many principles in XP. It is the core value of XP. Therefore, relatively speaking, TDD should be more easily promoted, and it is the highest in XP, and the highest output ratio is the highest. Just pay a small point, You can harvest up to you. This is also an extension of XP values. "Find the current most important issue, then solve it." The quality of the code may be the biggest problem we face now, so the application of TDD is the most valuable.