Java 修改 void 函数的输入参数，然后读取它
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Modify input parameter of a void function and read it afterwards
提问by Juan
I have a rather complex java function that I want to test using jUnit and I am using Mockito for this purpose. This function looks something like this:
我有一个相当复杂的 java 函数，我想使用 jUnit 进行测试，为此我正在使用 Mockito。这个函数看起来像这样：
public void myFunction (Object parameter){
...
doStuff();
...
convert(input,output);
...
parameter.setInformationFrom(output);
}
The function convert sets the attributes of output depending on input and it's a void type function, although the "output" parameter is what is being used as if it were returned by the function. This convert function is what I want to mock up as I don't need to depend on the input for the test, but I don't know how to do this, as I am not very familiar with Mockito.
函数 convert 根据输入设置输出的属性，它是一个 void 类型的函数，尽管“输出”参数是被使用的，就好像它是由函数返回的一样。这个转换函数是我想要模拟的，因为我不需要依赖于测试的输入，但我不知道如何做到这一点，因为我对 Mockito 不是很熟悉。
I have seen basic cases as when(something).thenReturn(somethingElse)or the doAnswer method which I understand is similar to the previous one but more logic can be added to it, but I don't think these cases are appropriate for my case, as my function does not have a return statement.
我已经看到了基本情况，when(something).thenReturn(somethingElse)或者我理解的 doAnswer 方法与前一个类似，但可以向其中添加更多逻辑，但我认为这些情况不适合我的情况，因为我的函数没有返回陈述。
采纳答案by Jeff Bowman
If you want the mocked method to call a method on (or otherwise alter) a parameter, you'll need to write an Answer as in this question ("How to mock a void return method affecting an object").
如果您希望被模拟的方法调用（或以其他方式更改）参数的方法，则需要编写一个答案，如本问题（“如何模拟影响对象的 void 返回方法”）。
From Kevin Welker's answerthere:
来自Kevin Welker的回答：
doAnswer(new Answer() {
Object answer(InvocationOnMock invocation) {
Object[] args = invocation.getArguments();
((MyClass)args[0]).myClassSetMyField(NEW_VALUE);
return null; // void method, so return null
}
}).when(mock).someMethod();
Note that newer best-practices would have a type parameter for Answer, as in Answer<Void>, and that Java 8's lambdas can compress the syntax further. For example:
请注意，较新的最佳实践将为 Answer 提供一个类型参数，如 中所示Answer<Void>，并且 Java 8 的 lambda 表达式可以进一步压缩语法。例如：
doAnswer(invocation -> {
Object[] args = invocation.getArguments();
((MyClass)args[0]).myClassSetMyField(NEW_VALUE);
return null; // void method in a block-style lambda, so return null
}).when(mock).someMethod();
