How do you use Testcontainers with Spring Boot for integration testing? इंटीग्रेशन टेस्टिंग के लिए स्प्रिंग बूट के साथ Testcontainers का उपयोग कैसे करें?

Testcontainers is a library that spins up real, disposable Docker containers (PostgreSQL, Kafka, Redis, etc.) for integration tests, so tests run against the actual database engine and SQL dialect used in production instead of an in-memory substitute like H2 that can behave subtly differently.

A container is declared as a static field annotated with @Container, its connection details are wired into Spring's environment via @DynamicPropertySource (or Spring Boot 3.1+'s @ServiceConnection), and the container starts once before all tests in the class and is torn down afterward, giving high-fidelity, isolated integration tests without needing a shared external database.

@SpringBootTest
@Testcontainers
class OrderRepositoryIT {
    @Container
    static PostgreSQLContainer<?> postgres = new PostgreSQLContainer<>("postgres:16");

    @DynamicPropertySource
    static void configure(DynamicPropertyRegistry registry) {
        registry.add("spring.datasource.url", postgres::getJdbcUrl);
    }
}