@SpringBootTest Purpose and Usage

Direct Answer

@SpringBootTest asks Spring Boot to create an ApplicationContext through SpringApplication for an integration test. It can discover the main Boot configuration and apply auto-configuration, but the beans and external connections actually created still depend on profiles, properties, mocks, exclusions, and webEnvironment. Use it when the behavior needs broad Boot wiring; use a plain unit test or a slice when that smaller boundary is enough.

Code Example

@SpringBootTest
@Transactional
class OrderServiceIntegrationTest {

    @Autowired
    private OrderService orderService;

    @Autowired
    private OrderRepository orderRepository;

    @Test
    void shouldCreateOrderAndPersistIt() {
        var order = new Order(null, "Laptop", 1200.00);
        var savedOrder = orderService.createOrder(order);

        assertThat(savedOrder.id()).isNotNull();
        assertThat(orderRepository.findById(savedOrder.id()))
            .isPresent()
            .get()
            .extracting(Order::item)
            .isEqualTo("Laptop");
    }
}

This verifies the real service-to-repository path present in this test context. @Transactional rolls back database work performed in the test-managed transaction.

Common Mistakes & Pitfalls

• Using @SpringBootTest for every test: A full Boot context is unnecessary for a pure function or a class whose collaborators can be supplied directly.
• Confusing MOCK with a running server: The default mode does not open a listening HTTP port. Use RANDOM_PORT or DEFINED_PORT for a real socket.
• Assuming automatic cleanup: Database changes are not rolled back merely because a test uses @SpringBootTest. Use a test-managed transaction where appropriate, or clean state explicitly. Remember that work committed in another thread, such as a real HTTP server request, is outside the test method's transaction.