Controller Layer Unit Testing

Question 1

MockMvc

Answer 1

MockMvc is a Spring MVC test framework that allows you to perform HTTP requests and assert the results. Provides methods to simulate GET, POST, PUT, DELETE, and other HTTP methods. Useful for testing request and response handling in the controller.

Question 2

@WebMvcTest

Answer 2

used for testing the controller layer in isolation. Loads only the specified controller and its related components, not the entire application context.

Question 3

@MockBean

Answer 3

@MockBean used in conjunction with @WebMvcTest to create and inject mock instances of dependencies (e.g., services) into the controller.

Question 4

Example

Answer 4

@WebMvcTest(UserController.class)
public class UserControllerTests {

@Autowired
private MockMvc mockMvc;

@MockBean
private UserService userService;

@Test
public void registerUserSuccess() throws Exception {
    // Prepare a valid UserDto request body
    String userDtoJson = "{\"name\": \"Test\", \"email\": \"test@gmail.com\"}";

    // Mock userService.registerUser to return a successful response
    when(userService.registerUser(any())).thenReturn(ResponseEntity.status(HttpStatus.CREATED).body("Success: User details successfully saved!"));

    // Perform POST request to /user/new with valid UserDto
    mockMvc.perform(MockMvcRequestBuilders.post("/user/new")
                    .contentType(MediaType.APPLICATION_JSON)
                    .content(userDtoJson))
            // Verify that the response status code is 201 create.
            .andExpect(MockMvcResultMatchers.status().isCreated())
            .andExpect(MockMvcResultMatchers.content().string("Success: User details successfully saved!"));
}

Question 5

@MockBean vs @Mock

Answer 5

@MockBean Replaces a bean in the Spring Application Context with a mock, so that the mock is injected anywhere the bean is used.
Provided by: Spring Boot’s spring-boot-test module.

@Mock
reates a mock instance without adding it to the Spring Application Context.
Provided by: Mockito