Mockito - NullPointerException

Question

I am trying to mock my AddressService using JUnit with Mockito, the class under test looks a bit like this;

    @Autowired
    private AddressDataManager addressDataManager;

    /**
     * Delegate AddressDataManager to add an individual Address object
     * @param address
     * @return Address object
     */
    public Address addAddress(Address address) {
        return this.addressDataManager.addAddress(address);
    }

Which then calls a JPA repository;

     /**
     * Create a new Address
     * 
     * @param address
     * @return JSON representation of an Address object
     */
    public Address addAddress(Address address) {
        addressRepo.save(address);
        return address;
    }

This issue is that I am getting a NullPointerException, when trying to create an Address result object using addAddress, which invokes the save() repository method call in my addressService class. It seems to be not returning the address object when I send an address object to it.

I have tried to;

• create a constructor with the AddressRepository and AddressDataManager in AddressManager
• Strangely, it works fine when I remove the @Mock addressRepository and AddressDataManager from the class and instead use AddressManager as the @Mock (instead of @InjectMocks). But I'm not sure that is the correct approach as some methods in AddressManager directly use the AddressRepository, so it should also create a NPE.

My Mockito test code:

@RunWith(MockitoJUnitRunner.class) 
public class AddressServiceTest {

    @Mock
    private AddressRepository addressRepo;

    @Mock
    private AddressDataManager addressDataManager;

    @InjectMocks
    private AddressManager addressService;

    public Address createTestData() {
        /** Create an Address **/
        Address mockAddress = new Address();
        /** Set fields **/
        mockAddress.setId((long) 1);
        mockAddress.setStreet("A Street");
        // ...
        return mockAddress;
    }

    /**
     * Test the addressService addAddress and addessRepo save method
     */
    @Test
    public void addAddressTest() {
        Address mockAddress = createTestData();
        /** Test the return type of save is indeed `Address` **/
        when(addressRepo.save(mockAddress)).thenReturn(mockAddress);    
        /** Create a returning result object to test addAddress method return **/
        Address addResult = addressService.addAddress(mockAddress); // NullPointerException here
        /** Check values are equal to address object **/
        assertEquals(Long.valueOf(1), addResult.getId());
        assertEquals("A Street", addResult.getStreet());
        // ...
        /** Verify that addressRepo save was called once using Mockito **/
        verify(addressRepo, times(1)).save(addResult); 
        verify(addressService, times(1)).addAddress(addResult);
    }

I feel like I am close, maybe I have the wrong tag over the wrong class? As I said, it worked well when I just used it like so;

@Mock
private AddressManager addressService;

/** Test the return type of addAddress is indeed `Address` **/
when(addressService.addAddress(mockAddress)).thenReturn(mockAddress);   
/** Verify that addressService addAddress was called once using Mockito **/
verify(addressService , times(1)).addAddress(addResult);