在单元测试静态类/方法/属性，停止与否 [英] Static class/method/property in unit test, stop it or not

问题描述

更新

应该静态类/方法/属性可以在单元测试开发环境中使用，因为它是没有办法对它进行测试，而不会引入包装，又是不可测试？

should a static class/method/property be used in a unit test development environment, given that it is no way to test it without introducing a wrapper that is again not testable?

另一种情况是，当静态成员单位测试目标内使用，静态memeber不能被嘲笑。因此，你必须测试静态meembers当单元测试目标的测试。你想，当静态成员进行运算将其隔离。

Another scenario is that when the static members are used within the unit tested target, the static memeber cannot be mocked. Thus, you have to test the static meembers when the unit tested target is tested. You want to isolate it when the static member performs calculation.

推荐答案

测试静态方法并不比测试任何其他方法不同。其静态方法作为的在另一个测试模块提出问题依赖的（因为它已经提到的 - 你不能嘲笑/提供免费的工具存根它）。但是，如果静态方法本身是单元测试，你可以简单地把它当作工作的，可靠的部件。

Testing static method is no different than testing any other method. Having static method as a dependency inside another tested module raises problems (as it's been mentioned - you can't mock/stub it with free tools). But if the static method itself is unit tested you can simply treat it as working, reliable component.

总体而言，没有什么错（如，它不会破坏单元测试/ TDD）与静态方法时：

Overall, there's nothing wrong (as in, it doesn't disrupt unit testing/TDD) with static methods when:

• 很简单，投入产出法（各种的计算该给的的）


• 是可靠的，按我们的意思是这是由你测试或者单位或来自第三方来源，你认为可靠的（如： Math.Floor 可能会被认为是可靠的 - 使用它不应该提出的你看出来，它是静态的！的警告，人们可能会认为微软，它的工作）

• it is simple, input-output method (all kinds of "calculate this given that")
• it is reliable, by what we mean it's either unit tested by you or comes from 3rd party source you consider reliable (eg. Math.Floor might be considered reliable - using it shouldn't raise "Look out, it's static!" warning; one might assume Microsoft does its job)

当静态方法会引起问题，应避免使用？基本上，只有当它们与/ 互动做一些你无法控制（或模拟）：

When static methods will cause problems and should be avoided? Basically only when they interact with/do something you cannot control (or mock):

• 各种文件系统，数据库，网络依赖


• 其他（可能更复杂）的静态方法从内部调用


• pretty任何东西嘲弄的框架，不能在普通条件处理

编辑： 何时静态方法的两个例子的会做单元测试的硬盘的

two examples on when static method will make unit testing hard

1

public int ExtractSumFromReport(string reportPath)
{
     var reportFile = File.ReadAllText(reportPath);
     // ...
}

你如何处理与 File.ReadAllText ？这显然​​会去的文件系统来检索文件的内容，这是重大的没有没有单元测试时。这是一个例子与外部的依赖静态方法。为了避免这种情况，你通常围绕创建文件系统API包装或简单地注入它作为依赖/委托。

How do you deal with File.ReadAllText? This will obviously go to file system to retrieve file content, which is major no-no when unit testing. This is example of static method with external dependency. To avoid that, you usually create wrapper around file system api or simply inject it as dependency/delegate.

2

public void SaveUser(User user)
{
    var session = SessionFactory.CreateSession();
    // ...
}

这个是什么？ Session是的非普通的依赖。当然，这可能来作为的Isession ，但怎么做力的SessionFactory 返回模拟？我们不能。我们不能创建的容易detemine 的会话对象无论是。

What about this? Session is non-trivial dependency. Sure, it might come as ISession, but how do force SessionFactory to return mock? We can't. And we can't create easy to detemine session object either.

在类似上述情况下，最好完全避免的静态方法。

In cases like above, it's best to avoid static methods altogether.

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