Null service response using mock test

I have a service that find a object in the repository and return one attribute of the object. I want try test service mocking access to repository, but when i call the service method return null.

My service:

@Service
public class MyService{

    public Object getModuleObj(String id, String module) {
        Object repObj = Repository.findOne(id,module);
        return repObj.getModule();
    }
}

My test class:

    @RunWith(SpringJUnit4ClassRunner.class)
    @WebMvcTest(MyController.class)
    @ContextConfiguration(classes = AnnotationConfigContextLoader.class)
    public class ApiTest {

        @MockBean
        public MyRepository repository;

        @MockBean
        private MyService service;

        @Test
        public void testGetObjectOfRepo() throws Exception {
            Object obj = new Object();
            Module mod = new Module();
            mod.setId("6");
            mod.setModule("test");
            obj.add(mod);

            /** mock repository response **/
            Mockito.when(repository.findOne("6","test")).thenReturn(obj);

            /** invoke service method**/
            String module= "test";
            /** serviceResponse return null **/
            Module serviceResponse = this.service.getModuleObj("6","test");
            Assert.assertEquals(mod, serviceResponse);
        }


        }

Comparison between objects fail because serviceResponse is null. It's correct as i'm mocking the repository?