SpringBoot Allow test config composition with Service Connections

ServiceConnectionContextCustomizerFactory looks for fields annotated with @ServiceConnection in the test class and test's parent classes.

As far as I could figure out, the only way to re-use @ServiceConnection annotated containers between tests is creating a base class with test containers declaration:

public abstract class IntegrationTest {

    @JdbcServiceConnection
    static PostgreSQLContainer postgres = new PostgreSQLContainer(DockerImageName.parse("postgres:15.1"));

   // alternatively @Testcontainers & @Container annotations from `junit-jupiter` can be used
    static {
        postgres.start();
    }
}

@SpringBootTest
class AppServiceConnectionStaticBaseClassTests extends IntegrationTest {

    @Test
    void contextLoads() {
    }
}

Spring, generally speaking supports test configuration composition through annotations or interfaces. I believe it would be nice if @ServiceConnection could be used in the same way. For example:

Annotations based composition

public class TestcontainersConfiguration {

    @JdbcServiceConnection
    static PostgreSQLContainer<?> postgres = new PostgreSQLContainer<>(DockerImageName.parse("postgres:15.1"));

    static {
        postgres.start();
    }
}

@SpringBootTest(classes = SpringBoot31DemoApplication.class)
@ContextConfiguration(classes = TestcontainersConfiguration.class)
class AppServiceConnectionCompositionTests {

    @Test
    void contextLoads(@Autowired JdbcTemplate jdbcTemplate) {
    }
}

Interface based composition

@Testcontainers
public interface WithContainers {

    @JdbcServiceConnection
    @Container
    PostgreSQLContainer postgres = new PostgreSQLContainer(DockerImageName.parse("postgres:15.1"));
}

@SpringBootTest
class AppServiceConnectionInterfaceCompositionTests implements WithContainers {

    @Test
    void contextLoads() {
    }
}

I've made a prototype of ServiceConnectionContextCustomizerFactory supporting configuration classes declared in @ContextConfiguration. I am pretty sure it does not cover all the edge cases but I hope it makes it clear what I have in mind.

https://github.com/maciej-scratches/spring-boot-3.1-service-connection-demo/blob/main/src/test/java/org/springframework/boot/test/autoconfigure/service/connection/CustomServiceConnectionContextCustomizerFactory.java

Comment From: philwebb

With #35022 pushed I think it should be possible to use standard @TestConfiguration for this. Something like:

@TestConfiguration
public class TestcontainersConfiguration {

    @Bean
    @ServiceConnection
    public PostgreSQLContainer<?> postgres() {
        return new PostgreSQLContainer<>(DockerImageName.parse("postgres:15.1"));
    }

}

@SpringBootTest(classes = SpringBoot31DemoApplication.class)
@Import(TestcontainersConfiguration.class)
class AppServiceConnectionCompositionTests {

    @Test
    void contextLoads(@Autowired JdbcTemplate jdbcTemplate) {
    }

}

I've not had a chance to actually test this yet.

Comment From: mhalbritter

Yep, this works, @philwebb, just tested it. Is this what you had in mind, @maciejwalkowiak ?

Comment From: maciejwalkowiak

Yes, exactly! Thanks!