java - Mockito 测试 - SimpMessageHeaderAccessor 不能由 getHeaders() 返回 getHeaders() 应该返回 MessageHeaders

Question

如何编写单元测试，因为它包括内部调用其他方法。

public class MyService implements UserDestinationResolver {

    @Override
    public UserDestinationResult myMethod(Message<?> message){
    SimpMessageHeaderAccessor accessor = MessageHeaderAccessor.getAccessor(message, SimpMessageHeaderAccessor.class);

****some logics to use access to get the return value UserDestinationResult***

    return UserDestinationResult;

这里的getAccessor是MessageHeaderAccessor类的一个静态方法

@Nullable
public static <T extends MessageHeaderAccessor> T getAccessor(Message<?> message, Class<T> requiredType) {
        return getAccessor(message.getHeaders(), requiredType);
    } 

这是我的测试用例:

@RunWith(MockitoJUnitRunner.class)
public class MyServiceTest {

    @Mock
    private Message<?> message;

    private SimpMessageHeaderAccessor accessor;

    @Mock
    private UserDestinationResult userDestinationResult;

    @InjectMocks
    private MyService myService;

    @Before
    public void set_up(){
        accessor = SimpMessageHeaderAccessor.wrap(message);
    }

    @Test
    public void resolveDestination(){
    when(MessageHeaderAccessor.getAccessor(message,
                SimpMessageHeaderAccessor.class)).thenReturn(accessor);

    """""""""""""""""""""""""""""""
    assertEquals(excepted, actual);
}

发生错误:

SimpMessageHeaderAccessor cannot be returned by getHeaders() getHeaders() should return MessageHeaders If you're unsure why you're getting above error read on. Due to the nature of the syntax above problem might occur because: 1. This exception might occur in wrongly written multi-threaded tests. Please refer to Mockito FAQ on limitations of concurrency testing. 2. A spy is stubbed using when(spy.foo()).then() syntax. It is safer to stub spies - - with doReturn|Throw() family of methods. More in javadocs for Mockito.spy() method.

Message是一个接口(interface)，我把它当成一个实例mock了，但是它根本获取不到headers，它是一个mock...我该如何解决这个问题..

Answer 1

您不能使用 vanilla mockito 模拟静态方法。

我建议在 MyService 中创建一个 protected 方法来包装静态调用，然后模拟它:

public class MyService implements UserDestinationResolver {

    @Override
    public UserDestinationResult myMethod(Message<?> message){
    SimpMessageHeaderAccessor accessor = getAccessor(message, SimpMessageHeaderAccessor.class);
     ...
    }

    protected SimpMessageHeaderAccessor getAccessor(Message<?> message, Class<T> requiredType){
         return SimpMessageHeaderAccessor.getAccessor(message, SimpMessageHeaderAccessor.class);
    }

然后在测试中:

@RunWith(MockitoJUnitRunner.class)
public class MyServiceTest {

    @Mock
    private Message<?> message;


    @Mock
    private UserDestinationResult userDestinationResult;

    @InjectMocks
    @Spy
    private MyService myService;

    @Before
    public void set_up(){
        accessor = SimpMessageHeaderAccessor.wrap(message);
    }

    @Test
    public void resolveDestination(){
       // Arrange
       doREturn(accessor).when(myService).getAccessor(message,
                SimpMessageHeaderAccessor.class));

      ....
}

这里的变化是您需要监视 MyService 才能模拟 protected 方法。