What are the advantages of using Testcontainers for application testing?

Testcontainers allows running real dependencies (such as databases, message brokers) in isolated Docker containers during testing. This offers several advantages:

• Realistic testing environment: tests work with actual services, not mocks, increasing reliability.
• Isolation of tests: each test can run its own container with a clean environment, avoiding conflicts and state influence.
• Ease of setup: no need to manually install and configure external services.
• Portability: tests work the same on different machines and CI servers with Docker.

Example of using PostgreSQL:

@Container
public PostgreSQLContainer<?> postgres = new PostgreSQLContainer<>("postgres:13")
    .withDatabaseName("testdb")
    .withUsername("user")
    .withPassword("pass");

@Test
void testDatabaseConnection() {
    String url = postgres.getJdbcUrl();
    // Use url for connection and testing
}