June 2021
Intermediate to advanced
290 pages
9h 21m
Chinese
Content preview from Node与Express开发（第2版）
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质量保证
｜
43
注意，“关于”页的功能和服务器错误页的测试需要比别的页做更多的工作。“关于”页调
用
render
函数时传入了
fortune
（幸运饼），因此我们增加了一个断言，即
render
函数会获
得一个
fortune
，而
fortune
是至少包含一个字符的字符串
。完整地阐述
Jest
的功能以及它
的
expect
方法超出了本书的范畴，你可以从
Jest
的主页找到详尽的文档。注意，服务器错
误处理函数接收
4
个而不是
2
个参数，所以需要提供更多的模拟对象。
5.7.4
测试维护
你可能意识到了测试不是一劳永逸的事。例如，如果因为某些原因你重命名了“
home
”视
图，那么测试就会失败，除了修复代码之外，还需要修正这个测试。
因此，团队要花很多精力考虑待测试目标以及测试内容，并设置切合实际的断言。例如，
我们不需要检查“关于”页是否获得了一个
fortune
变量，如果丢弃“幸运饼”这个特性，
就不需要修正这个测试了。
而且，你的代码究竟要测试到什么程度，我也没法提供太多的建议。不过我认为，航空设
备或医疗设备的测试代码和市场营销网站的测试代码应该有截然不同的标准。
我可以提供给你的是如何回答“我的代码有多少被测试到了？”这个问题，答案就是接下
来要讨论的
代码覆盖率
。
5.7.5
代码覆盖率
对于你的代码有多少被测试到了这个问题，代码覆盖率提供了一个量化的答案，但是就像
编程中的很多问题一样，其实是没有简单答案的。
Jest
提供了一些
代码覆盖率自动化的分析，这对我们很有帮助。要查看有多少代码被测试
到了，可以运行以下命令：
npm test ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.