Java Testing Tutorials

Mockito is a popular Java mocking framework used in unit tests. It lets you create mock objects, stub method return values, and verify interactions — without needing a real database or external service.

@Mock creates a mock instance of a class or interface. @InjectMocks creates a real instance of the class under test and automatically injects all @Mock fields into it via constructor, setter, or field injection.

Annotate your test class with @ExtendWith(MockitoExtension.class), declare your dependencies with @Mock, annotate the class under test with @InjectMocks, then use when(...).thenReturn(...) to stub behavior and verify(...) to assert interactions.

MockMvc is a Spring Test utility that lets you test your Spring MVC controllers without starting a real HTTP server. Used with @WebMvcTest, it lets you perform and assert HTTP requests (GET, POST, etc.) entirely in-memory.