How to mock an asynchronous (@Async) method in Spring Boot using Mockito?

Question

What is the best way to mock an asynchronous ( @Async) method with mockito? The service provided below:

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

Mockito check as below:

@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));
    } 
}

The verification method shouldVerifyabove will always throw:

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.

The exception above will not happen if I remove @Asyncfrom the method TaskService.createTask.

Spring Boot Version: 1.4.0.RELEASE

Mockito Version: 1.10.19

Answer 1

It was found that by changing the Async mode to AspectJ, the problem was fixed:

@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);
    }
}

, , .

Answer 2

Spring Boot, 1.4.1. , TaskService , Mockito.

, TaskService . @Async , .

- :

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
    }

}