Mockito: How to properly mock a List of Spring Services

Question

I have the following Spring Service class that I'm trying to test with Mockito:

@Service
public class ObjectExportService {

    @Autowired
    protected List<SecuredService<? extends SecuredObject>> securedServices;

    public void doStuff() {
        for(int i = 0; i < this.securedServices.size(); i++){
            SecuredService<? extends SecuredObject> securedSrv = this.securedServices.get(i);
            //this access works
        }
        for (SecuredService<? extends SecuredObject> securedSrv : this.securedServices) { //this access does not work
            
        }
    }
}

This is my Test class for that service:

@RunWith(MockitoJUnitRunner.class)
public class ObjectExportServiceTest {

    @InjectMocks
    private ObjectExportService objectExportService;

    @Mock
    protected List<SecuredService<? extends SecuredObject>> securedServices;

    @Test
    public void testDoStuff(){
        objectExportService.doStuff();
        Assert.assertTrue(true);
    }
}

When I run the test, I get a NullpointerException, but only in the for-each loop.

First I assumed is a similar problem as described in this thread: I have Mocked the List and would therefore need to mock the iterator() call.

The solutions provided in that thread didn't work for me, because I am actually autowiring a List.

Bishares · Accepted Answer · 2021-03-27T06:21:27.027

So I stumbled across this solution in another thread. Simply changing the @Mock to @Spy resolved the issue for me:

@RunWith(MockitoJUnitRunner.class)
public class ObjectExportServiceTest {

    @InjectMocks
    private ObjectExportService objectExportService;

    @Spy  // <-- change here
    protected List<SecuredService<? extends SecuredObject>> securedServices;

    @Test
    public void testDoStuff(){
        objectExportService.doStuff();
        Assert.assertTrue(true);
    }
}

Mockito: How to properly mock a List of Spring Services

1 Answers1