the first day of studying agile principles

结对编程（Pair Programming）是一种敏捷软件开发实践，指两个程序员并排坐在一台电脑前，面对同一个显示器，使用同一个键盘和鼠标一起工作.

 

the test-driven development

the three rules of TDD:

1. You are not allowed to write any production code unless it is to make a failing unit test pass.

在写完“红色”（无法通过测试）的单元测试代码之前，不允许写任何的产品代码。

2. You are not allowed to write any more of a unit test than is sufficient to fail; and compilation failures are failures.

除了恰好让单元测试失败的代码（编译错误也是错误的一种），不要写更多的单元测试。

3. You are not allowed to write any more production code than is sufficient to pass the one failing unit test.

所写产品代码应该刚刚能够满足单元测试。