@MockBean 正在返回空对象

Question

我正在尝试使用@MockBean； java版本11，Spring Framework版本（5.3.8），Spring Boot版本（2.5.1）和Junit Jupiter（5.7.2）。

    @SpringBootTest
    public class PostEventHandlerTest {
        @MockBean
        private AttachmentService attachmentService;

        @Test
        public void handlePostBeforeCreateTest() throws Exception {
            Post post = new Post("First Post", "Post Added", null, null, "", "");
            
            Mockito.when(attachmentService.storeFile("abc.txt", "")).thenReturn(new Attachment());
     
            PostEventHandler postEventHandler = new PostEventHandler();
            postEventHandler.handlePostBeforeCreate(post);
            verify(attachmentService, times(1)).storeFile("abc.txt", "");
       }
    }

    @Slf4j
    @Component
    @Configuration
    @RepositoryEventHandler
    public class PostEventHandler {
           @Autowired
           private AttachmentService attachmentService;

           @Autowired
           private PostRepository postRepository;

           public void handlePostBeforeCreate(Post post) throws Exception {
             ...
             /* Here attachmentService is found null when we execute above test*/
             attachmentService.storeFile(fileName, content);
             ...
           }
    }

attachmentService 没有被模拟，它返回 null

Answer 1

我认为你误解了 Mocks 的用法。

@MockBean 确实创建了一个 mock（内部使用 Mockito）并将这个 bean 放到应用程序上下文中，以便它可以用于注入等。

但是，作为程序员，您有责任指定当您在此模拟上调用一种或另一种方法时，您期望从该模拟返回什么。

所以，假设你的AttachementService 有一个方法String foo(int)：

public interface AttachementService { // or class 
   public String foo(int i);
}

您应该在 Mockito API 的帮助下指定期望：

    @Test
    public void handlePostBeforeCreateTest() throws Exception { 
        // note this line, its crucial
        Mockito.when(attachmentService.foo(123)).thenReturn("Hello");

        Post post = new Post("First Post", "Post Added", null, null, "", "");
        PostEventHandler postEventHandler = new PostEventHandler();
        postEventHandler.handlePostBeforeCreate(post);
        verify(attachmentService, times(1)).storeFile("", null);
   }

如果您不指定期望值并且您的被测代码在某个时候调用foo，则此方法调用将返回null