使用 Mockito 调用回调

您希望设置一个执行此操作的对象。看看Mockito文档，在 https://static.javadoc.io/org.mockito/mockito-core/2.8.47/org/mockito/Mockito.html#answer_stubsAnswer

你可以写这样的东西

when(mockService.doAction(any(Request.class), any(Callback.class))).thenAnswer(
    new Answer<Object>() {
        Object answer(InvocationOnMock invocation) {
            ((Callback<Response>) invocation.getArguments()[1]).reply(x);
            return null;
        }
});

（当然，用它应该是什么来代替）x

考虑使用 ArgumentCaptor，它在任何情况下都与“grab[bing] 回调对象”更匹配。

/**
 * Captor for Response callbacks. Populated by MockitoAnnotations.initMocks().
 * You can also use ArgumentCaptor.forClass(Callback.class) but you'd have to
 * cast it due to the type parameter.
 */
@Captor ArgumentCaptor<Callback<Response>> callbackCaptor;

@Test public void testDoAction() {
  // Cause service.doAction to be called

  // Now call callback. ArgumentCaptor.capture() works like a matcher.
  verify(service).doAction(eq(request), callbackCaptor.capture());

  assertTrue(/* some assertion about the state before the callback is called */);

  // Once you're satisfied, trigger the reply on callbackCaptor.getValue().
  callbackCaptor.getValue().reply(x);

  assertTrue(/* some assertion about the state after the callback is called */);
}

虽然当回调需要立即返回（读取：同步）时，an 是一个好主意，但它也引入了创建匿名内部类的开销，并且不安全地将元素从转换为所需的数据类型。它还要求您从答案中对系统的预回调状态进行任何断言，这意味着您的答案的大小和范围可能会增加。Answerinvocation.getArguments()[n]

相反，请异步处理回调：使用 ArgumentCaptor 捕获传递给服务的回调对象。现在，您可以在测试方法级别进行所有断言，并在选择时进行调用。如果您的服务负责多个并发回调，这将特别有用，因为您可以更好地控制回调返回的顺序。reply