mockito：有没有一种方法来捕获stubbed方法的返回值？

Question

如果我嘲笑一种方法来返回某个对象的新实例，我该如何捕获返回的实例？

例如为：

when(mock.someMethod(anyString())).thenAnswer(new Answer() { 
    Object answer(InvocationOnMock invocation) { 
     Object[] args = invocation.getArguments(); 
     Object mock = invocation.getMock(); 
     return new Foo(args[0]) 
    } 
}); 

很显然，我可以有Foo类型的字段，而里面answer其设置到新的实例，但有一个更好的办法吗？像ArgumentCaptor？

Answer 1

看起来要观察然后Answer实例和接收notfications每个answer方法被调用的时候（这将触发新Foo创建）。那么，为什么不发明一种ObservableAnswer类：

public abstract class ObservableAnswer implements Answer { 
    private Listener[] listeners; // to keep it very simple... 

    public ObservableAnswer(Listener...listeners) { 
    this.listeners = listeners; 
    } 

    @Override 
    public Object answer(InvocationOnMock invocation) { 
    Object answer = observedAnswer(invocation); 
    for (Listener listener:listeners) { 
     listener.send(answer); 
    } 
    return answer; 
    } 

    // we'll have to implement this method now 
    public abstract Object observedAnswer(InvocationOnMock invocation); 
} 

用途：

Listener[] myListenerns = getListeners(); // some magic (as usual) 
when(mock.someMethod(anyString())).thenAnswer(new ObservableAnswer(myListeners) { 
    Object observedAnswer(InvocationOnMock invocation) { 
     Object[] args = invocation.getArguments(); 
     Object mock = invocation.getMock(); 
     return new Foo(args[0]) 
    } 

}); 

Answer 2

我想要做类似的事情，但有窥探的对象，而不是模仿。具体来说，给定一个窥探对象，我想捕获返回值。根据Andreas_D的回答，这是我想出来的。

public class ResultCaptor<T> implements Answer { 
    private T result = null; 
    public T getResult() { 
     return result; 
    } 

    @Override 
    public T answer(InvocationOnMock invocationOnMock) throws Throwable { 
     result = (T) invocationOnMock.callRealMethod(); 
     return result; 
    } 
} 

预期用法：

// spy our dao 
final Dao spiedDao = spy(dao); 
// instantiate a service that does some stuff, including a database find 
final Service service = new Service(spiedDao); 

// let's capture the return values from spiedDao.find() 
final ResultCaptor<QueryResult> resultCaptor = new ResultCaptor<>(); 
doAnswer(resultCaptor).when(spiedDao).find(any(User.class), any(Query.class)); 

// execute once 
service.run(); 
assertThat(resultCaptor.getResult()).isEqualTo(/* something */); 

/// change conditions /// 

// execute again 
service.run(); 
assertThat(resultCaptor.getResult()).isEqualTo(/* something different */);