Java Tests

In Java testing (especially with JUnit and Mockito), annotations are used to mark test methods, configure lifecycle events, inject mocks, and more.

Here’s a comprehensive list of commonly used annotations in Java tests:

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✅ JUnit Annotations

▶️ Core Test Annotations

Annotation	Purpose	Example
@Test	Marks a method as a test	@Test void testAddition() { ... }
@BeforeEach	Runs before each test method	@BeforeEach void setUp() { ... }
@AfterEach	Runs after each test method	@AfterEach void tearDown() { ... }
@BeforeAll	Runs once before all test methods	@BeforeAll static void init() { ... }
@AfterAll	Runs once after all test methods	@AfterAll static void cleanup() { ... }
@Disabled	Disables a test or test class	@Disabled("Broken test")

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▶️ Assertions and Parameterized Tests

Annotation	Purpose
@DisplayName	Sets a custom name for the test
@ParameterizedTest	Runs the same test with different inputs
@ValueSource	Supplies literal values for parameterized tests
@CsvSource, @MethodSource	Provide complex parameter sets

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✅ Mockito Annotations

Annotation	Purpose
@Mock	Creates a mock object
@InjectMocks	Injects mock fields into the test subject
@Spy	Creates a spy (partial mock)
@Captor	Declares an ArgumentCaptor
@MockBean	(Spring) Mocks a bean in Spring context

🔧 Enable Mockito Annotations

In JUnit 5, add this to your test class:

@ExtendWith(MockitoExtension.class)
public class MyServiceTest { ... }

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✅ Spring Boot Test Annotations

Annotation	Purpose
@SpringBootTest	Loads full Spring context
@WebMvcTest	Tests Spring MVC controllers only
@DataJpaTest	Tests JPA repositories
@MockBean	Replaces a Spring bean with a mock
@Autowired	Injects dependencies

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🧪 Example

@ExtendWith(MockitoExtension.class)
class UserServiceTest {

    @Mock
    UserRepository userRepository;

    @InjectMocks
    UserService userService;

    @BeforeEach
    void setUp() {
        // setup code
    }

    @Test
    void testFindUser() {
        when(userRepository.findById(1L)).thenReturn(Optional.of(new User("Alice")));
        User result = userService.findUser(1L);
        assertEquals("Alice", result.getName());
    }
}

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