A question about JdbiTestcontainersExtension and "schema/user/database" creation

[stoyants]

(when I say schema below, it can mean also user or database, depends of the database provider)

In this post @hgschmie gave a brief explanation of the idea to create schemata in a separate thread and this way minimize the wait time of the tests. This is implemented in TestcontainersDatabaseInformationSupplier.

If I understand it correctly, expectation is that if there are N tests in a test class, N+1 schemata will be created - one for each test and last one might remain unused.

But somehow I can't create an example where it is working as designed.

In test classes JdbiExtension members should be annotated as @RegisterExtension and it can be either Static Field or an Instance Field

When it is a static, 2 schemata are created, first is reused and provided to each test and second never comes in play.

import java.util.List;

import org.jdbi.v3.core.statement.Query;
import org.jdbi.v3.testing.junit5.JdbiExtension;
import org.junit.jupiter.api.RepeatedTest;
import org.junit.jupiter.api.extension.RegisterExtension;
import org.testcontainers.containers.JdbcDatabaseContainer;
import org.testcontainers.containers.PostgreSQLContainer;
import org.testcontainers.junit.jupiter.Container;
import org.testcontainers.junit.jupiter.Testcontainers;
import org.testcontainers.utility.DockerImageName;

import static org.assertj.core.api.Assertions.assertThat;

@Testcontainers
class StaticJdbiExtensionSchemaTest {
    private static final List<String> preinstalledSchemata = List.of("public", "pg_catalog", "pg_toast", "information_schema");
    @Container
    static JdbcDatabaseContainer<?> dbContainer = new PostgreSQLContainer<>(DockerImageName.parse("postgres:13-alpine"));
    @RegisterExtension
    static JdbiExtension extension = JdbiTestcontainersExtension.instance(dbContainer);

    @RepeatedTest(5)
    void testPostgresSchemas() {
        List<String> schemaNames = extension.getJdbi().withHandle(h -> {
            try (Query query = h.createQuery("SELECT schema_name FROM information_schema.schemata")) {
                return query.mapTo(String.class).list();
            }
        });
        schemaNames.removeAll(preinstalledSchemata);
        assertThat(schemaNames).hasSize(2);
    }
}

When it is an instance, 2 schemata are created for each test, as a new extension instance is created for each test. First schema is used by the test and second is never used.

import java.util.List;

import org.jdbi.v3.core.statement.Query;
import org.jdbi.v3.testing.junit5.JdbiExtension;
import org.junit.jupiter.api.RepeatedTest;
import org.junit.jupiter.api.RepetitionInfo;
import org.junit.jupiter.api.extension.RegisterExtension;
import org.testcontainers.containers.JdbcDatabaseContainer;
import org.testcontainers.containers.PostgreSQLContainer;
import org.testcontainers.junit.jupiter.Container;
import org.testcontainers.junit.jupiter.Testcontainers;
import org.testcontainers.utility.DockerImageName;

import static org.assertj.core.api.Assertions.assertThat;

@Testcontainers
public class InstanceJdbiExtensionSchemaTest {
    private static final List<String> preinstalledSchemata = List.of("public", "pg_catalog", "pg_toast", "information_schema");
    @Container
    static JdbcDatabaseContainer<?> dbContainer = new PostgreSQLContainer<>(DockerImageName.parse("postgres:13-alpine"));
    @RegisterExtension
    JdbiExtension extension = JdbiTestcontainersExtension.instance(dbContainer);

    @RepeatedTest(5)
    void testPostgresSchemas(RepetitionInfo repetitionInfo) {
        List<String> schemaNames = extension.getJdbi().withHandle(h -> {
            try (Query query = h.createQuery("SELECT schema_name FROM information_schema.schemata")) {
                return query.mapTo(String.class).list();
            }
        });
        schemaNames.removeAll(preinstalledSchemata);
        assertThat(schemaNames).hasSize(2 * repetitionInfo.getCurrentRepetition());
    }
}

So, the tests either share the schema (in case of static extension) or always "wait" for a new schema (in case of instance field extension) .

I also configured some tests to run in parallel, with instance extension, but the result is the same - number of schemata created is 2 * number of tests. Parallel test with static extension are even dangerous - they run in the same schema and can interfere with each other.

The question is: is there an example, where the design from the above post works as explained?