如何使用 Mockito 在 Spring Boot 中模拟异步（@Async）方法？

Question

用 mockito 模拟异步 (@Async) 方法的最佳方法是什么？提供以下服务：

@Service
@Transactional(readOnly=true)
public class TaskService {
    @Async
    @Transactional(readOnly = false)
    public void createTask(TaskResource taskResource, UUID linkId) {
        // do some heavy task
    }
}

Mockito 的验证如下：

@RunWith(SpringRunner.class)
@WebMvcTest(SomeController.class)
public class SomeControllerTest {
    @Autowired
    MockMvc mockMvc;
    @MockBean    
    private TaskService taskService;
    @Rule
    public MockitoRule mockitoRule = MockitoJUnit.rule();

    // other details omitted...

    @Test
    public void shouldVerify() {
        // use mockmvc to fire to some controller which in turn call taskService.createTask
        // .... details omitted
        verify(taskService, times(1)) // taskService is mocked object
            .createTask(any(TaskResource.class), any(UUID.class));
    } 
}

上面的测试方法shouldVerify总是会抛出：

org.mockito.exceptions.misusing.InvalidUseOfMatchersException: 
Misplaced argument matcher detected here:

-> at SomeTest.java:77) // details omitted
-> at SomeTest.java:77) // details omitted 

You cannot use argument matchers outside of verification or stubbing.
Examples of correct usage of argument matchers:
    when(mock.get(anyInt())).thenReturn(null);
    doThrow(new RuntimeException()).when(mock).someVoidMethod(anyObject());
    verify(mock).someMethod(contains("foo"))

Also, this error might show up because you use argument matchers with methods that cannot be mocked.
Following methods *cannot* be stubbed/verified: final/private/equals()/hashCode().
Mocking methods declared on non-public parent classes is not supported.

如果我从TaskService.createTask 方法中删除@Async，则不会发生上述异常。

Spring Boot 版本：1.4.0.RELEASE

Mockito 版本：1.10.19

Answer 1

发现通过将异步模式更改为 AspectJ 解决了这个问题：

@EnableCaching
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(lazyInit = true) 
@EnableAsync(mode = AdviceMode.ASPECTJ) // Changes here!!!
public class Main {
    public static void main(String[] args) {
        new SpringApplicationBuilder().sources(Main.class)
                                    .run(args);
    }
}

在我了解此问题的真正根本原因之前，我会接受这是一个临时的黑客解决方案。

Answer 2

我们希望在 1.4.1 中修复 bug in Spring Boot。问题是您的模拟 TaskService 仍然被异步调用，这会破坏 Mockito。

您可以通过为TaskService 创建一个接口并创建一个模拟来解决此问题。只要您只在实现上留下@Async 注释，事情就会起作用。

类似这样的：

public interface TaskService {

    void createTask(TaskResource taskResource, UUID linkId);

}

@Service
@Transactional(readOnly=true)
public class AsyncTaskService implements TaskService {

    @Async
    @Transactional(readOnly = false)
    @Override
    public void createTask(TaskResource taskResource, UUID linkId) {
        // do some heavy task
    }

}