16.5 Perfect Integration Test Environments with Testcontainers

Testing with H2 in-memory DB can lead to false positives — tests pass but fail in production due to SQL syntax differences and constraint variations between H2 and real databases. Testcontainers spins up real Docker containers during tests, providing a perfectly identical DB environment.

1. Adding Dependencies

testImplementation 'org.springframework.boot:spring-boot-testcontainers'
testImplementation 'org.testcontainers:junit-jupiter'
testImplementation 'org.testcontainers:mysql'

2. @SpringBootTest + Testcontainers Integration Test

@SpringBootTest
@Testcontainers
class OrderIntegrationTest {

    @Container
    static MySQLContainer<?> mysql = new MySQLContainer<>("mysql:8.0")
            .withDatabaseName("testdb")
            .withUsername("test")
            .withPassword("test");

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

    @Autowired
    private OrderService orderService;

    @Autowired
    private UserRepository userRepository;

    @Test
    @DisplayName("Order creation is persisted correctly to the real DB.")
    @Transactional
    void create_order_integration() {
        User user = userRepository.save(new User("test", "test@example.com"));
        Long orderId = orderService.createOrder(new CreateOrderRequest(user.getId(), 1L, 2));
        assertThat(orderId).isNotNull().isPositive();
    }
}

3. Testcontainers + Redis

@Container
static GenericContainer<?> redis = new GenericContainer<>("redis:7.0")
        .withExposedPorts(6379);

@DynamicPropertySource
static void configureRedis(DynamicPropertyRegistry registry) {
    registry.add("spring.data.redis.host", redis::getHost);
    registry.add("spring.data.redis.port", () -> redis.getMappedPort(6379));
}