XP简单设计之我见 - 杨栋 - 博客园 https://www.cnblogs.com/yangdong/archive/2011/03/01/my-point-view-of-xp-simple-design.html
极限编程对于简单设计的四条规则 - CSDN博客 https://blog.csdn.net/ibelieve1974/article/details/54880262
XP Rules of Simple Design
1. Runs all the tests.
The code must do what is needed. Why bother if it does not?
代码必须符合需求，用测试保证它是符合需求的。
2. Expresses every idea that we need to express.
The code should be self-documenting, communicating the intention
of the programmer.
Code简单易懂
3. Says everything once and only once.
Duplication must be removed so that as things change, the same
idea does not have to be changed in numerous places.
没有重复代码
4. Has no superfluous parts.
This final rule prevents us from putting in things that are not yet
needed.
不要提前Design暂不需要的需求。这样会减慢当前开发，不确定需求还会带来不确定的麻烦。