In a project where I work, we have been initializing Services for Unit testing in the following way:
- Mock dependencies that are needed for the Service.
- Create the Service using a constructor.
Something like this :
@RunWith(SpringRunner.class)
public class ServiceTest extends AbstractUnitTest {
@Mock private Repository repository;
private Service service;
@Before
public void init() {
service = new Service(repository);
when(repository.findById(any(Long.class))).thenReturn(Optional.of(new Entity()));
}
}
But our new developer proposed to use @Autowired and @SpringBootTest
@SpringBootTest(classes = ServiceTest.class)
@MockBean(classes = Repository.class)
@RunWith(SpringRunner.class)
public class ServiceTest extends AbstractUnitTest {
@MockBean private Repository repository;
@Autowired private Service service;
@Before
public void init() {
when(repository.findById(any(Long.class))).thenReturn(Optional.of(new Entity()));
}
}
Before that, I supposed that @Autowired and @SpringBootTest should be used only in integration tests. But googled a lot and I see that some people use those two in Unit tests.
I read boot-features-testing. Also, I read this Unit tests vs integration tests with Spring.
For me, it still doesn`t feel well that we need to involve Spring to do dependency injection for unit tests, as we can do this by ourselves to do the unit testing.
So, should @Autowired and @SpringBootTest be used in unit tests?
No. A unit test is to test a single component in isolation. Using constructor injection in your beans allows you to very simply call new SomeService(myMock), no Spring required.
Writing component or functional tests (testing your application but not wiring it up to external services for a full integration test, mocking only external interfaces; this is good for things like MockMvc tests) is a good match for @SpringBootTest, and in that case you may need to create mock objects in a Spring configuration and autowire them into your test so you can manipulate them.