Unit testing helps a lot in projects that are larger than any one developer can hold in their head. They allow you to run the unit test suite before checkin and discover if you broke something. This cuts down a lot on instances of having to sit and twiddle your thumbs while waiting for someone else to fix a bug they checked in, or going to the hassle of reverting their change so you can get some work done. It's also immensely valuable in refactoring, so you can be sure that the refactored code passes all the tests that the original code did.

我同意与大多数人相反的观点: 不编写单元测试是可以的 特别是重原型的编程(例如AI)很难与单元测试相结合。

我在几年前发现了TDD，从那时起我就使用它编写了所有我喜欢的项目。我估计，TDD一个项目所花费的时间与牛仔式地组合一个项目所花费的时间大致相同，但我对最终产品的信心增加了，以至于我忍不住有一种成就感。

我还觉得它改进了我的设计风格(更面向界面，以防我需要一起模拟东西)，而且，正如顶部的绿色帖子所写的，它有助于“编码便秘”:当你不知道接下来要写什么，或者你有一个令人生畏的任务摆在你面前时，你可以写小一点的。

最后，我发现到目前为止，TDD最有用的应用是在调试中，如果仅仅因为您已经开发了一个询问框架，那么您就可以用它来刺激项目以可重复的方式产生错误。

One of the best things about unit testing is that your code will become easier to test as you do it. Preexisting code created without tests is always a challenge because since they weren't meant to be unit-tested, it's not rare to have a high level of coupling between classes, hard-to-configure objects inside your class - like an e-mail sending service reference - and so on. But don't let this bring you down! You'll see that your overall code design will become better as you start to write unit-tests, and the more you test, the more confident you'll become on making even more changes to it without fear of breaking you application or introducing bugs.

There are several reasons to unit-test your code, but as time progresses, you'll find out that the time you save on testing is one of the best reasons to do it. In a system I've just delivered, I insisted on doing automated unit-testing in spite of the claims that I'd spend way more time doing the tests than I would by testing the system manually. With all my unit tests done, I run more than 400 test cases in less than 10 minutes, and every time I had to do a small change in the code, all it took me to be sure the code was still working without bugs was ten minutes. Can you imagine the time one would spend to run those 400+ test cases by hand?

当涉及到自动化测试——无论是单元测试还是验收测试——每个人都认为编写可以手动完成的代码是浪费精力，有时这是真的——如果你计划只运行一次测试的话。自动化测试最好的部分是，您可以毫不费力地运行它们几次，并且在第二次或第三次运行之后，您所浪费的时间和精力已经得到了补偿。

最后一个建议是，不仅要对代码进行单元测试，还要先进行测试(详见TDD和BDD)。

使用单元测试套件，可以在保持其余功能不变的情况下对代码进行更改。这是一个很大的优势。当你完成新功能的编码时，你会使用单元测试套件和回归测试套件吗?

单元测试的一个好处是，它们可以作为说明代码行为方式的文档。好的测试有点像参考实现，团队成员可以通过查看它们来了解如何将他们的代码与您的代码集成。