如何使用 Mockito 模拟 void 方法 [英] How to mock void methods with Mockito

问题描述

如何使用 void 返回类型模拟方法?

How to mock methods with void return type?

我实现了一个观察者模式，但我不能用 Mockito 模拟它，因为我不知道如何.

I implemented an observer pattern but I can't mock it with Mockito because I don't know how.

然后我试图在互联网上找到一个例子，但没有成功.

And I tried to find an example on the Internet but didn't succeed.

我的班级是这样的:

public class World {

    List<Listener> listeners;

    void addListener(Listener item) {
        listeners.add(item);
    }

    void doAction(Action goal,Object obj) {
        setState("i received");
        goal.doAction(obj);
        setState("i finished");
    }

    private string state;
    //setter getter state
} 

public class WorldTest implements Listener {

    @Test public void word{
    World  w= mock(World.class);
    w.addListener(this);
    ...
    ...

    }
}

interface Listener {
    void doAction();
}

系统不是通过模拟触发的.

The system is not triggered with mock.

我想显示上面提到的系统状态.并根据它们做出断言.

I want to show the above-mentioned system state. And make assertions according to them.

推荐答案

看一看 Mockito API 文档.正如链接文档中提到的(第 12 点)，您可以使用任何 doThrow()、doAnswer()、doNothing()、doReturn() 来自 Mockito 框架的方法系列，用于模拟 void 方法.

Take a look at the Mockito API docs. As the linked document mentions (Point # 12) you can use any of the doThrow(),doAnswer(),doNothing(),doReturn() family of methods from Mockito framework to mock void methods.

例如

Mockito.doThrow(new Exception()).when(instance).methodName();

或者如果您想将其与后续行为结合起来，

or if you want to combine it with follow-up behavior,

Mockito.doThrow(new Exception()).doNothing().when(instance).methodName();

假设您正在考虑在下面的类 World 中模拟 setter setState(String s) 是代码使用 doAnswer 方法来模拟 setState.

Presuming that you are looking at mocking the setter setState(String s) in the class World below is the code uses doAnswer method to mock the setState.

World mockWorld = mock(World.class); 
doAnswer(new Answer<Void>() {
    public Void answer(InvocationOnMock invocation) {
      Object[] args = invocation.getArguments();
      System.out.println("called with arguments: " + Arrays.toString(args));
      return null;
    }
}).when(mockWorld).setState(anyString());

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