Write Unit test in SpringBoot Without start application

Question

Am developing MicroServices in springBoot. Am writing unit test for Service and DAO layer. When I use @SpringBootTest it starting application on build. But It should not start application when I run unit test. I used @RunWith(SpringRunner.class), But am unable to @Autowired class instance in junit class. How can I configure junit test class that should not start application and how to @Autowired class instance in junit class.

Answer 1

With Spring Boot you can start a sliced version of your application for your tests. This will create a Spring Context that only contains a subset of your beans that are relevant e.g. only for your web layer (controllers, filters, converters, etc.): @WebMvcTest.

There is a similar annotation that can help you test your DAOs as it only populates JPA and database relevant beans (e.g. EntitiyManager, Datasource, etc.): @DataJpaTest.

If you want to autowire a bean that is not part of the Spring Test Context that gets created by the annotatiosn above, you can use a @TestConfiguration to manually add any beans you like to the test context

@WebMvcTest(PublicController.class)
class PublicControllerTest {

  @Autowired
  private MockMvc mockMvc;

  @TestConfiguration
  static class TestConfig {

    @Bean
    public EntityManager entityManager() {
      return mock(EntityManager.class);
    }

    @Bean
    public MeterRegistry meterRegistry() {
      return new SimpleMeterRegistry();
    }

  }
}

Answer 2

Use MockitoJUnitRunner for JUnit5 testing if you don't want to start complete application.

Any Service, Repository and Interface can be mocked by @Mock annotation.

@InjectMocks is used over the object of Class that needs to be tested.

Here's an example to this.

@RunWith(MockitoJUnitRunner.class)
@SpringBootTest
public class AServiceTest {
    
    @InjectMocks
    AService aService;
    
    @Mock
    ARepository aRepository;
    
    @Mock
    UserService userService;
    
    
    @Before
    public void setUp() {
        // MockitoAnnotations.initMocks(this);
        // anything needs to be done before each test.
    }
    
    @Test
    public void loginTest() {
        Mockito.when(aRepository.findByUsername(ArgumentMatchers.anyString())).thenReturn(Optional.empty());
        String result = aService.login("test");
        assertEquals("false", result);
    }