单元测试 vs 集成测试，你该怎么选？

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在1998年，Kent Beck编写了sUnit，一个面向SmallTalk的单元测试框架。之后，他将这个框架移植到Java，即jUnit。从那时起，xUnit框架扩展到那些最流行的编程语言。比较新的语言，如Golang和Rust，已经将测试直接合并到编译器和标准库中。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https:\/\/static001.geekbang.org\/infoq\/2e\/2ea6f42b29f3067adea10c6df993a393.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"但是单元测试并不是唯一。还有集成测试和性能测试等等。在我看来，集成测试和单元测试是健壮软件的基石。因此，今天让我们看看单元测试与集成测试之间的区别，以及你什么时候该选择哪种测试。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"什么是一个单元？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https:\/\/static001.geekbang.org\/infoq\/75\/752da7164ec2eacb17d04442c84df420.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":"center","origin":null},"content":[{"type":"text","text":"一个单元是逻辑上分离的最小代码块"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"单元测试是一种孤立地测试尽可能小的代码片段的测试。那么，什么是一个单元？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"术语“单元”来自数学。数字1被认为是单元，因为它是最小的自然数。它是最小的正整数。以此类推，你源代码的一个单元就是逻辑上与其余代码分离的最小代码片段。它是一个完整的且逻辑上不同的代码片段，而且是最小的部分。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在大多数编程语言中，你的单元会是一个函数或方法调用。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"单元测试的好处是，如果你的代码由独立的小片段组成，那么，为它们编写测试就相当容易。这种易编写性意味着你可以在开发功能时完成单元测试。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"与其它形式的测试相比，单元测试的执行时间相当短。这意味着你可以频繁运行单元测试。随着软件的成熟，一套单元测试是防止回归和降低维护成本的有力工具。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"追溯单元测试"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在考虑将单元测试添加到现有软件时，需要考虑成本和收益。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"单元测试的一个关键假设是，被测试的软件很容易分成不同的单元。在没有考虑单元测试编写的软件中，这个假设很少成立。向现有软件添加单元测试通常是一种非常好的方法，来稳定软件并防止将来回归，但是重构代码来支持简单的单元测试可能需要大量工作，甚至会引入新的缺陷。在考虑将单元测试添加到现有软件时，需要考虑成本和收益。如果你的代码正在工作，如果代码很少需要修改，如果代码不容易进行单元测试，那么加入单元测试的好处可能无法保证成本。在这些情况下，可以依靠集成测试来防止该领域的缺陷。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"什么是集成测试?"}]},{"type":"image","attrs":{"src":"https:\/\/static001.geekbang.org\/infoq\/d9\/d9be70604d99357a75f4fb699cf0c869.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":"center","origin":null},"content":[{"type":"text","text":"集成测试聚焦于整个软件栈"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果单元测试的哲学是基于这样一种认识，即测试小的独立代码片段是防止回归的一种好方法，那么集成测试是基于这样一种理解，即事情通常在边缘状态出错。外部世界是一个混乱的地方，它与你代码交互的地方通常是意外发生的地方。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你可以通过单元测试实现100%代码覆盖率，但仍然发现你的软件失败。你可能试图从错误的位置读取文件，或者你的软件可能从一个调用的服务得到预期之外的输出，或者它可能以一种无效的方式调用数据库。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"尽管单元测试应该快速运行并且数量众多，但是一个好的集成测试策略应该关注较少数量的高影响测试。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这些测试应该跨越单元测试无法跨越的所有界限，写入文件系统，接触外部资源，等等。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"当集成测试棘手时"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"某些外部系统确实很难集成到测试中。这是因为它们在现实世界中有着无法消除的副作用：金融交易、电子邮件发送、物理移动一个喷漆机器人等。在你在测试中放弃并避开它们之前，找找解决方案。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"许多外部系统有一个文档化的方法来在集成测试中使用它们。支付处理程序通常有测试信用卡号，可以设置具有测试邮箱账户的测试用户来测试邮件发送。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"集成测试越接近真实世界的交互，就越有可能发现问题并提供真正的价值。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Amazon SES——"},{"type":"link","attrs":{"href":"https:\/\/docs.aws.amazon.com\/ses\/latest\/DeveloperGuide\/send-email-simulator.html","title":"","type":null},"content":[{"type":"text","text":"Test email addresses"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Paypal——"},{"type":"link","attrs":{"href":"https:\/\/developer.paypal.com\/docs\/payflow\/payflow-pro\/payflow-pro-testing\/","title":"","type":null},"content":[{"type":"text","text":"Test credit card numbers"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"UPS——"},{"type":"link","attrs":{"href":"https:\/\/www.ups.com\/us\/en\/help-center\/sri\/developer-instruct.page","title":"","type":null},"content":[{"type":"text","text":"Test api mode"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"一个电子商务例子"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"假设你正在编写一个简单的电商网站，一个简化版的amazon.com。这里的细节很重要，所以我们假设，你会使用PostgreSQL作为你的数据存储，使用PayPal进行支付，使用UPS进行发货、使用Amazon Simple Email Service来发送电子发票邮件。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"单元测试："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"单元测试策略将以一种孤立的方式测试应用程序的逻辑。这可能包括："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"测试税费计算逻辑是否正确地计算出各个司法管辖区的税费"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"测试放置到购物车数据结构中的项目是否被正确添加"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"测试折扣代码是否被正确使用"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这些领域中的每一个都可能有几个测试。每个测试将验证一小部分功能。单元测试的能力来自它们的数量、简单性以及它们的执行速度和便捷性。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"集成测试："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"另一方面，你的集成测试将专注于测试你的电子商务代码与其它系统的交互。这意味着不仅要测试与数据存储的集成，还要测试与邮件发送服务的集成、与支付服务的集成等等。这些可能包括："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"测试是否可以从外部运输服务中检索运输费率"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"测试发票是否可以生成并正确发送"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"测试订单信息是否可以持久化并从数据存储中正确检索"}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"测试交易是否可以发送并被支付处理程序正确处理"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这些功能中的每一个都可能需要一个或两个集成测试来验证。这些测试运行起来会比较慢，可能涉及一些安装和拆卸步骤。结果是，每个测试的代码覆盖率会相当大。这些测试将通过捕获单元测试不能捕获的问题来产生价值。然而，维护成本和执行时间可能会比较高。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"集成测试 vs 单元测试"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https:\/\/static001.geekbang.org\/infoq\/cb\/cbc91858e0f7fd898084bc1977c70974.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":"center","origin":null},"content":[{"type":"text","text":"是时候正面比较了"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"那么，应该首选哪种类型的测试呢？单靠两者中的任一个都是不够的。这两者都是综合测试计划的一部分。让我们直接比较一下："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https:\/\/static001.geekbang.org\/infoq\/02\/02a33f645ea12f88a33855ce8df2415b.jpeg","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"基于理想化测试的工作软件"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"每种情况都是独特的，基于在其它情况下有效的建议不应盲目遵循。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"现在我们明白了，单元测试不应该触及文件系统，而集成测试应该只集成松散的组件。但实际上，将测试划分为两个明确的类别有点太简单了，如果我们只关注定义，我们就会忽略目标，即正确的工作软件。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一些非常有想法的开发者认为"},{"type":"link","attrs":{"href":"https:\/\/dhh.dk\/2014\/tdd-is-dead-long-live-testing.html","title":"","type":null},"content":[{"type":"text","text":"单元测试可以并且应该读写数据库"}]},{"type":"text","text":"。其它人则认为单元测试是一种浪费，粗粒度的集成测试提供的价值最大。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"问题是，每种情况都是独特的，基于在其它情况下有效的建议不应盲目遵循。需要牢记的一个问题是，这个测试要捕获什么类型的缺陷。如果每个测试都是经过深思熟虑编写来提升软件可靠性的，如果测试在不再有价值时被删除，那么随着时间的推移，将发现为特定项目提供最大价值的特定测试方法。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"原文链接："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https:\/\/blog.earthly.dev\/unit-vs-integration\/","title":null,"type":null},"content":[{"type":"text","text":"https:\/\/blog.earthly.dev\/unit-vs-integration\/"}]}]}]}