我看到很多问题都在问“如何”用一种特定的语言进行单元测试,但没有人问“什么”、“为什么”和“什么时候”。

是什么? 它对我有什么用? 我为什么要用它? 什么时候用(什么时候不用)? 有哪些常见的陷阱和误解


当前回答

在单元测试和TDD的哲学优势方面,这里有一些关键的“灯泡”观察,这些观察在我试探性地走上TDD启蒙之路的第一步时打动了我(没有原创或一定是新闻)……

TDD does NOT mean writing twice the amount of code. Test code is typically fairly quick and painless to write and is a key part of your design process and critically. TDD helps you to realize when to stop coding! Your tests give you confidence that you've done enough for now and can stop tweaking and move on to the next thing. The tests and the code work together to achieve better code. Your code could be bad / buggy. Your TEST could be bad / buggy. In TDD you are banking on the chances of BOTH being bad / buggy being fairly low. Often its the test that needs fixing but that's still a good outcome. TDD helps with coding constipation. You know that feeling that you have so much to do you barely know where to start? It's Friday afternoon, if you just procrastinate for a couple more hours... TDD allows you to flesh out very quickly what you think you need to do, and gets your coding moving quickly. Also, like lab rats, I think we all respond to that big green light and work harder to see it again! In a similar vein, these designer types can SEE what they're working on. They can wander off for a juice / cigarette / iphone break and return to a monitor that immediately gives them a visual cue as to where they got to. TDD gives us something similar. It's easier to see where we got to when life intervenes... I think it was Fowler who said: "Imperfect tests, run frequently, are much better than perfect tests that are never written at all". I interprete this as giving me permission to write tests where I think they'll be most useful even if the rest of my code coverage is woefully incomplete. TDD helps in all kinds of surprising ways down the line. Good unit tests can help document what something is supposed to do, they can help you migrate code from one project to another and give you an unwarranted feeling of superiority over your non-testing colleagues :)

这篇演讲很好地介绍了测试所需要的所有内容。

其他回答

在单元测试和TDD的哲学优势方面,这里有一些关键的“灯泡”观察,这些观察在我试探性地走上TDD启蒙之路的第一步时打动了我(没有原创或一定是新闻)……

TDD does NOT mean writing twice the amount of code. Test code is typically fairly quick and painless to write and is a key part of your design process and critically. TDD helps you to realize when to stop coding! Your tests give you confidence that you've done enough for now and can stop tweaking and move on to the next thing. The tests and the code work together to achieve better code. Your code could be bad / buggy. Your TEST could be bad / buggy. In TDD you are banking on the chances of BOTH being bad / buggy being fairly low. Often its the test that needs fixing but that's still a good outcome. TDD helps with coding constipation. You know that feeling that you have so much to do you barely know where to start? It's Friday afternoon, if you just procrastinate for a couple more hours... TDD allows you to flesh out very quickly what you think you need to do, and gets your coding moving quickly. Also, like lab rats, I think we all respond to that big green light and work harder to see it again! In a similar vein, these designer types can SEE what they're working on. They can wander off for a juice / cigarette / iphone break and return to a monitor that immediately gives them a visual cue as to where they got to. TDD gives us something similar. It's easier to see where we got to when life intervenes... I think it was Fowler who said: "Imperfect tests, run frequently, are much better than perfect tests that are never written at all". I interprete this as giving me permission to write tests where I think they'll be most useful even if the rest of my code coverage is woefully incomplete. TDD helps in all kinds of surprising ways down the line. Good unit tests can help document what something is supposed to do, they can help you migrate code from one project to another and give you an unwarranted feeling of superiority over your non-testing colleagues :)

这篇演讲很好地介绍了测试所需要的所有内容。

如果你想使用Kent Beck推广的TDD方法开发项目,像NUnit、xUnit或JUnit这样的库是必须的:

你可以阅读《测试驱动开发介绍》(TDD)或Kent Beck的《测试驱动开发:举例说明》。

然后,如果你想确保你的测试覆盖了代码中“好的”部分,你可以使用NCover、JCover、PartCover或其他软件。它们会告诉你代码的覆盖率。取决于你对TDD的熟练程度,你会知道你是否已经很好地练习了它:)

首先,无论是谈论单元测试还是其他类型的自动化测试(集成、加载、UI测试等),与您所建议的关键区别在于它是自动化的、可重复的,并且不需要消耗任何人力资源(=没有人需要执行测试,它们通常按下按钮就可以运行)。

测试驱动开发在某种程度上取代了单元测试这个术语。作为一个老手,我会提到它的更一般的定义。

单元测试还意味着测试一个较大系统中的单个组件。这个组件可以是dll、exe、类库等。它甚至可以是多系统应用程序中的单个系统。因此,单元测试最终是对一个更大系统的单个部分进行测试。

然后,您可以通过测试所有组件如何一起工作来进行集成测试或系统测试。

单元测试,粗略地说,就是在与测试代码隔离的情况下测试代码。我想到的直接优势是:

测试的运行变得自动化和可重复 您可以在更细粒度的级别上进行测试,而不是通过GUI进行点击测试

请注意,如果您的测试代码写入文件、打开数据库连接或在网络上执行某些操作,则更适合将其归类为集成测试。集成测试是一件好事,但不应将其与单元测试混淆。单元测试代码应该简短、简单且易于执行。

另一种看待单元测试的方法是先编写测试。这被称为测试驱动开发(简称TDD)。TDD带来了额外的优势:

您不需要编写推测性的“我将来可能需要这个”代码——只要能够通过测试即可 您编写的代码总是会被测试覆盖 通过先编写测试,您不得不考虑如何调用代码,从长远来看,这通常会改善代码的设计。

如果你现在还没有做单元测试,我建议你现在就开始做。找一本好书,实际上任何xUnit-book都可以,因为它们之间的概念可以很好地转换。

有时编写单元测试会很痛苦。当出现这种情况时,试着找个人来帮助你,并抵制住“只写该死的代码”的诱惑。单元测试很像洗碗。这并不总是令人愉快的,但它让你的比喻厨房保持干净,而你真的希望它干净。:)


编辑:我想到了一个误解,虽然我不确定它是否普遍。我曾听一个项目经理说过,单元测试让团队把所有的代码都写了两次。如果它看起来和感觉是那样的,那么,你做错了。编写测试通常不仅可以加快开发速度,而且还为您提供了一个方便的“现在我完成了”指示器,否则您就不会有这个指示器。