(我假设您使用的是功能测试"，是指涉及整个系统或应用程序正在运行的测试.)

(I'm assuming that you're using "functional test" to mean a test involving the whole system or application being up and running.)

出于以下三个原因，我将对我编写的 new 功能进行单元测试:

I would unit test new functionality as I wrote it, for three reasons:

• 它可以帮助我更快地使用工作代码.通常，单元测试失败，修复代码，单元测试通过"的周转时间比功能测试失败，修复代码，功能测试通过"的时间短了 .
• 这可以帮助我以更简洁的方式设计代码
• 它可以帮助我理解我的代码以及维护代码的意图.如果我进行更改，它将使我更加自信自己没有损坏任何东西.

(这包括错误修复，如Epaga所建议.)

(This includes bug fixes, as suggested by Epaga.)

我强烈推荐迈克尔·费瑟斯(Michael Feathers)的有效地与传统一起工作代码" ，为您提供有关如何开始对不是针对其设计的代码库进行单元测试的提示.

I would strongly recommend Michael Feathers' "Working Effectively with Legacy Code" to give you tips on how to start unit testing a codebase which wasn't designed for it.