What does @SpringBootTest do and when should you use it? @SpringBootTest क्या करता है और इसका उपयोग कब करना चाहिए?

@SpringBootTest bootstraps the complete Spring application context for a test, the same way the real application would start, including all auto-configuration, beans, and (optionally) an embedded web server via webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT. This makes it the go-to annotation for true end-to-end integration tests.

Because it loads the entire context, @SpringBootTest is significantly slower than a sliced test like @WebMvcTest or a plain unit test, and Spring caches the context across test classes with identical configuration to reduce repeated startup cost. It should be reserved for tests that genuinely need the full wiring — most tests are better served by a narrower slice annotation or Mockito-based unit tests.

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
class OrderApplicationTests {
    @Autowired private TestRestTemplate restTemplate;

    @Test
    void createOrder_returns201() {
        ResponseEntity<Order> response = restTemplate.postForEntity("/api/orders", request, Order.class);
        assertEquals(HttpStatus.CREATED, response.getStatusCode());
    }
}