@SpringBootTest vs Slice Tests Spring Boot | Java Fresher

Direct Answer

@SpringBootTest builds a broad application context from the application's Spring Boot configuration. Its default webEnvironment is MOCK, so it does not start a live server unless you choose RANDOM_PORT or DEFINED_PORT. A slice such as @WebMvcTest or @DataJpaTest limits configuration to one layer. Pick the narrowest context that proves the behavior.

Code Example

// Broad context, but no live server with the default MOCK web mode
@SpringBootTest
class ApplicationWiringTest { }

// MVC slice with a context-level service replacement
@WebMvcTest(OrderController.class)
class OrderControllerTest {
    @Autowired MockMvc mvc;
    @MockitoBean OrderService service;
}

// Broad context plus a live server
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
class HttpIntegrationTest { }

Common Mistakes & Pitfalls

• Calling the default an end-to-end test: @SpringBootTest uses a mock web environment unless configured otherwise.
• Assuming a slice has all application beans: slices intentionally restrict scanning and auto-configuration.
• Using the broadest context for simple logic: a direct unit test is clearer when Spring behavior is irrelevant.
• Mocking the feature under test: a repository query test needs the repository and database, not a mocked repository.
• Ignoring context reuse: inconsistent properties and bean overrides can create different cache keys.