@WebMvcTest for controller testing in JUnit - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @WebMvcTest annotation in Spring Boot testing?

@WebMvcTest is used to test Spring MVC controllers specifically. It loads only the web layer components, making tests faster and focused on controller behavior without starting the full application context.

intermediate

Which Spring components are loaded by default when using @WebMvcTest?

Only the web layer components like controllers, @ControllerAdvice, Jackson converters, and related MVC components are loaded. Services, repositories, and other beans are not loaded unless explicitly mocked.

intermediate

How do you mock a service dependency in a @WebMvcTest controller test?

You use @MockBean to create a mock of the service and inject it into the controller. This way, the controller can call the mock service during the test.

beginner

What is the role of MockMvc in @WebMvcTest?

MockMvc allows you to perform HTTP requests to the controller endpoints in tests without starting a server. It simulates web requests and verifies responses.

beginner

Why is @WebMvcTest preferred over @SpringBootTest for controller testing?

@WebMvcTest loads only the web layer, making tests faster and more focused. @SpringBootTest loads the full application context, which is slower and not necessary for controller unit tests.

What does @WebMvcTest load by default?

A Only Spring MVC controllers and related web components

B The full Spring application context

C Only service and repository beans

D No beans, only configuration

@WebMvcTest loads only the web layer components like controllers and MVC infrastructure, not the full context.

How do you provide a mock service to a controller in a @WebMvcTest?

A Using <code>@Autowired</code>

B Using <code>@MockBean</code>

C Using <code>@Service</code>

D Using <code>@Component</code>

@MockBean creates and injects a mock bean into the Spring context for testing.

Which class is used to simulate HTTP requests in @WebMvcTest?

A RestTemplate

B TestRestTemplate

C MockMvc

D WebClient

MockMvc simulates HTTP requests to controller endpoints without starting a server.

Why might @WebMvcTest tests run faster than @SpringBootTest tests?

A Because it loads only the web layer, not the full application context

B Because it runs tests in parallel automatically

C Because it uses a real database

D Because it disables logging

Loading only the web layer reduces startup time and resource usage, making tests faster.

If a controller depends on a service, but you forget to mock the service in a @WebMvcTest, what will happen?

A The controller will ignore the service

B The test will pass without errors

C The service will be automatically created

D The test will fail with a <code>NoSuchBeanDefinitionException</code>

Since @WebMvcTest does not load service beans, missing mocks cause bean not found errors.

Explain how @WebMvcTest helps in testing Spring MVC controllers and how you handle dependencies like services.

Think about isolating the controller from other layers.

Describe the difference between @WebMvcTest and @SpringBootTest when testing a Spring Boot application.

Consider scope and speed of tests.