Injecting mocks with Mockito does not work

You can create package level setter for mUserInfoService in CreateMailboxService class.

@Service
public class CreateMailboxService {   
    @Autowired UserInfoService mUserInfoService; // this should be mocked
    @Autowired LogicService mLogicService;  // this should be autowired by Spring

    public void createMailbox() {
        // do mething
        System.out.println("test 2: " + mUserInfoService.getData());
    }

    void setUserInfoService(UserInfoService mUserInfoService) {
        this.mUserInfoService = mUserInfoService;
    }
}

Then, you can inject that mock in the test using the setter.

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "file:src/main/webapp/WEB-INF/spring/root-context.xml" })
public class CreateMailboxServiceMockTest {

    @Mock
    UserInfoService mUserInfoService;

    CreateMailboxService mCreateMailboxService;

    @Before
    public void setup() {
        MockitoAnnotations.initMocks(this);
        mCreateMailboxService = new CreateMailboxService();
        mCreateMailboxService.setUserInfoService(mUserInfoService);
    }

    ...
}

This way you can avoid problems with @InjectMocks and Spring annotations.

If you are trying to use the @Mock annotation for a test that relies directly on Spring injection, you may need to replace @Mock with @MockBean @Inject (both annotations), and @InjectMocks with @Inject. Using your example:

@MockBean
@Inject
UserInfoService mUserInfoService;

@Inject
CreateMailboxService mCreateMailboxService;

For those who stumbles on this thread and are running with JUnit 5 you need to replace @RunWith(SpringJUnit4ClassRunner.class)

with

@ExtendWith(MockitoExtension.class)
@RunWith(JUnitPlatform.class)

Further reading here. Unfortunately there is no hint when executing the test cases with JUnit 5 using the old annotation.

In my case, I had a similar issue when I worked with JUnit5

@ExtendWith(MockitoExtension.class)
class MyServiceTest {
...

@InjectMocks
MyService underTest;

@Test
void myMethodTest() {
...
}

underTest was null. The cause of the problem was that I used @Test from JUnit4 package import org.junit.Test; instead JUnit5 import org.junit.jupiter.api.Test;