Question

I am writing unit tests for service layer in my spring application.
Here is my service class

    @Service
    public class StubRequestService implements RequestService {    
        @Autowired
        private RequestDao requestDao;  

        @Transactional(propagation = Propagation.REQUIRED, readOnly = true)
        @Override
        public Request getRequest(Long RequestId) {
            Request dataRequest = requestDao.find(requestId);
            return dataRequest;
        }
    }  

Here is my test class

@RunWith(MockitoJUnitRunner.class)
@ContextConfiguration(locations = { "/META-INF/spring/applicationContext.xml" })
public class StubRequestServiceTest {

    @Mock
    public RequestDao requestDao;

    StubRequestService stubRequestService;  // How can we Autowire this ?

    @org.junit.Before
    public void init() {
      stubRequestService = new StubRequestService();  // to avoid this 
      stubRequestService.setRequestDao(dataRequestDao);  
      // Is it necessary to explicitly set all autowired elements ?  
      // If I comment/remove above setter then I get nullPointerException 
    }

    @Test
    public void testGetRequest()  {
        Request request = new Request();
        request.setPatientCnt("3");
        when(requestDao.find(anyLong())).thenReturn(request);
        assertEquals(stubRequestService.getRequest(1234L).getPatientCnt(),3);
    }    
}   

Its working fine but I have few questions

1. How can we Autowire service class in test ? I am using constructor in init() method to create service object.
2. Do we have to set all Autowire element for service class ? For ex StubRequestService have autowired RequestDao which I need to set explicitly before calling test method otherwise it giveds nullPointerException as requestDao is null in StubRequestService.getRequest method.
3. Which are the good practices to follow while unit testing Spring service layer ? (If I am doing anything wrong).

Answer 1

1. If you really feel that it will make your tests easier to understand – you can initialize a spring context and fetch all of the objects from there. However, usually it will require creating a separate spring configuration XML file specifically for tests therefore I would not recommend it.

   ApplicationContext applicationContext = new ClassPathXmlApplicationContext("testApplicationContext.xml");
   stubRequestService = (RequestService)applicationContext.getBean("myRequestServiceBean");
   

2. (and 3) Basically, I prefer testing each component of my application in total isolation from eachother and that’s why I do not recommend what I described in [1].

What that means, is you take a separate logical slice of your application and test only it, while fully mocking up everything it tries to access.

Let’s say you have three classes:

//Fetches stuff from some webservice and converts to your app domain POJOs
class DataAccessLayer {
    public void setWebservice(Webservice ws) {...};

    public MyObject getMyObject() {...};
}

//Formats the domain POJOs and sends them to some kind of outputstream or stuff.
class ViewLayer {
    public void setOutputStream(OutputStream os) {...};

    public void viewMyObject(MyObject mo) {...};
}

//Main entry point of our MyObject fetch-process-display workflow
class Controller {
    public void setDataAccessLayer(DataAccessLayer dal) {...};
    public void setViewLayer(ViewLayer vl) {...};

    public void showMyObject() {
        MyObject mo = dal.getMyObject();
        ...some processing here maybe...
        vl.viewMyObject(mo);
    }
}

Now, what tests can we write here?

1. Test if DataAccessLayer properly converts the object from mocked up WS to our domain object.
2. Test if ViewLayer properly formats the object given to him and writes it to mocked up output stream.
3. Test if Controller takes an object from mocked up DataAccessLayer processes it properly and sends it to mocked up ViewLayer.