TDD can be useful, but there are other simple principles that you can keep in mind while writing your tests last and still reach a clean and entirely testable piece of code.

• 测试驱动开发是有用的，但在编写测试代码的时候，还有其它一些简 单的原则你必须铭记于心，你必须保证测试代码干净并且同样可测。