# Use the JUnit 5 extension for more control


If the special JDBC URL doesn't meet your needs, or you need more control over
container creation (for example, to copy initialization scripts), use the
Testcontainers JUnit 5 extension:

```java
@DataJpaTest
@TestPropertySource(properties = {
    "spring.test.database.replace=none"
})
@Testcontainers
class ProductRepositoryTest {

  @Container
  static PostgreSQLContainer postgres =
    new PostgreSQLContainer("postgres:16-alpine")
      .withCopyFileToContainer(
        MountableFile.forClasspathResource("sql/init-db.sql"),
        "/docker-entrypoint-initdb.d/init-db.sql");

  @DynamicPropertySource
  static void configureProperties(DynamicPropertyRegistry registry) {
    registry.add("spring.datasource.url", postgres::getJdbcUrl);
    registry.add("spring.datasource.username", postgres::getUsername);
    registry.add("spring.datasource.password", postgres::getPassword);
  }

  @Autowired
  ProductRepository productRepository;

  @Test
  @Sql("/sql/seed-data.sql")
  void shouldGetAllProducts() {
    List<Product> products = productRepository.findAll();
    assertEquals(2, products.size());
  }

  @Test
  @Sql("/sql/seed-data.sql")
  void shouldNotCreateAProductWithDuplicateCode() {
    Product product = new Product(3L, "p101", "Test Product");
    productRepository.createProductIfNotExists(product);
    Optional<Product> optionalProduct = productRepository.findById(
      product.getId()
    );
    assertThat(optionalProduct).isEmpty();
  }
}
```

This approach:

- Uses `@Testcontainers` and `@Container` to manage the container lifecycle.
- Copies `init-db.sql` into the container's init directory so PostgreSQL
  runs it at startup.
- Uses `@DynamicPropertySource` to register the container's connection details
  with Spring Boot.
- Tests PostgreSQL-specific features like `ON CONFLICT DO NOTHING` that
  wouldn't work with H2.

## Summary

- Use the **special JDBC URL** (`jdbc:tc:postgresql:...`) for the quickest way
  to switch from H2 to a real database — it's a one-property change.
- Use the **JUnit 5 extension** when you need more control over the container
  (custom init scripts, environment variables, etc.).
- Both approaches work with Spring Data JPA (`@DataJpaTest`) and JdbcTemplate
  (`@JdbcTest`) tests.

## Further reading

- [Testcontainers Postgres module](https://java.testcontainers.org/modules/databases/postgres/)
- [Testcontainers JDBC support](https://java.testcontainers.org/modules/databases/jdbc/)
- [Testing a Spring Boot REST API with Testcontainers](/guides/testcontainers-java-spring-boot-rest-api/)