如何模拟返回最终类的静态方法? [英] How to mock static method that returns final class?

问题描述

我想模拟下一行:

Bigquery bigquery = Transport.newBigQueryClient(options).build();

这里的问题是newBigQueryClient方法返回的Bulder类是最终的.这意味着我既不能使用嘲笑者也不可以使用powermockito来嘲笑它(它返回这样的异常:不能对最终类进行子类化)，但是我需要返回适合于在其上模仿构建方法的东西.有什么想法怎么做吗?

The problem here is that newBigQueryClient method returns Bulder class, which is final. This means that I cannot mock it neither with mockito or powermockito(it returns such exception: Cannot subclass final class), but I need to return something suitable to mock build method on it. Any ideas how to do it?

推荐答案

关于改善代码并使其更具可测试性的建议:

A suggestion to improve your code and making it much more testable:

首先，您不会像您作为示例给出的作业那样模拟语句.您可以模拟对象，并将其引用分配给其类型表示超类型的变量.

First of all, you do not mock a statement like the assignment that you gave us as an example. You mock objects and assign their references to variables whose type represent a super type.

此外，如果您觉得自己必须嘲笑某些东西，那么您显然已经在代码段中找到了一个重要的依赖项.

Additionally, if you feel you have to mock something away, you have obviously found a dependency in your code snippet that is an important concept.

使这个概念显而易见！

在您的情况下，您想要获取一个Bigquery对象并将其引用分配给变量.不清楚的概念是某人必须提供这样的对象.

In your case, you want to get a Bigquery object and assign its reference to a variable. The unclear concept is that someone has to provide such an object.

通过界面使这个概念更清楚:

Make this concept clear with an interface:

interface BigqueryProvider {
    Bigquery provide(Object options);
}

在课堂上你也有陈述

Bigquery bigquery = Transport.newBigQueryClient(options).build();

您现在添加以下实例变量

you now add the following instance variable

private final BigqueryProvider bigqueryProvider;

，并相应地更改构造函数.正如我所说的，它必须在构造时设置.当然，您还必须标识调用构造函数的代码.为此，您还需要一个默认实现:

and change your constructors accordingly. As I made it final it must be set at construction time. Of course, you must also identify the code where you call the constructors. For that you also need a default implementation:

final class DefaultBigqueryProvider implements BigqueryProvider {
    @Override
    public Bigquery provide(Object options) {
        return Transport.newBigQueryClient(options).build();
    }
}

然后将上述分配更改为

Bigquery bigquery = bigqueryProvider.provide(options);

现在进行测试:现在，在测试中，您可以为提供程序接口提供测试实现.一个模拟框架可以轻松地为您做到这一点.您还可以返回选择的Bigquery对象，无论该对象是该类还是子类的对象，都没有关系.

Now to the tests: In your tests, you now can provide a test implementation for the provider interface. A mocking framework can easily do that for you. You are also able to return a Bigquery object of your choice, being it an object of that class or of a subclass, it doesn't matter.

然后，您的测试代码通过为您提供完全受控的模拟BigqueryProvider来实例化您的类.

Your test code then instantiates your class by providing them a mocked BigqueryProvider which you have under full control.

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