Why does Testcontainers not use application.properties / application.yaml?

Question

In my Spring Boot 2.4.3 application I use Testcontainers and I followed the instructions found on the internet. I have an application.yaml:

spring:
  datasource:
    url: jdbc:tc:postgresql:13.2:///testdb?TC_INITSCRIPT=tc_initscript_postgresql.sql
    username: duke
    password: s3crEt
  jpa:
    database-platform: org.hibernate.dialect.PostgreSQL95Dialect
    hibernate:
      ddl-auto: create-drop

but when I debug the application the container has always 'test' as the value for URL, username and password.

Here's my test class:

@ActiveProfiles("test")
@Testcontainers
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public abstract class AbstractApplicationIT {

    final static DockerImageName POSTGRES_IMAGE = DockerImageName.parse("postgres:13.2-alpine");

        @Container
    //    public static GenericContainer postgreSQLContainer = new GenericContainer(POSTGRES_IMAGE)
        public static PostgreSQLContainer<?> postgreSQLContainer = new PostgreSQLContainer<>(POSTGRES_IMAGE)
    //            .withInitScript("tc_initscript_postgresql.sql")
    //            .withPassword("password")
    //            .withUsername("username")
    //            .withDatabaseName("test")
    //            .withInitScript("tc_initscript_postgresql.sql")
                ;
    
    //    @DynamicPropertySource
    //    static void postgresqlProperties(DynamicPropertyRegistry registry) {
    //        registry.add("spring.datasource.url", postgreSQLContainer::getJdbcUrl);
    //        registry.add("spring.datasource.password", postgreSQLContainer::getPassword);
    //        registry.add("spring.datasource.username", postgreSQLContainer::getUsername);
    //    }
    
        @Test
        public void contextLoads() {
            System.out.println(postgreSQLContainer.getDatabaseName());
            System.out.println(postgreSQLContainer.getUsername());
            System.out.println(postgreSQLContainer.getPassword());
        }
    
    }

The System.out:

test
test
test

...even without using @DynamicPropertySource.

Answer 1

The container don't know the application.properties.

application.properties is Spring Boot configuration and have nothing to do with Testcontainers.

You can override values like this

@Container
private PostgreSQLContainer postgresqlContainer = new PostgreSQLContainer()
    .withDatabaseName("foo")
    .withUsername("foo")
    .withPassword("secret");

You can also read the values from the application.properties like this:

@Value("spring.datasource.username")
private String username;