This sample project shows different ways to set up reliable integration tests with Spring Boot, Flyway, and Testcontainers. All other technologies used (JDBC, PostgreSQL, JUnit 5) are interchangeable: Using, for example, Hibernate, MariaDB, and TestNG is possible with the same techniques.

All approaches guarantee that all test cases are independent (start with a fresh database) and do not hide errors (like database rollbacks). Furthermore, the test classes can be executed concurrently¹ to take advantage of multicore processors. What varies, however, is their execution speed and how much custom plumbing is necessary.

• FlywayMigrationStrategyAuthorRepositoryTest.java uses only facilities provided by Spring Boot but is the slowest (100% runtime).
• FlywayMigrationAuthorRepositoryTest.java requires a TestExecutionListener but is significantly faster than the previous approach (~70% runtime).
• DatabaseDumpAuthorRepositoryTest.java uses a dynamically generated SQL dump to initialise the database. This is the fastest approach (~50% runtime) and stays fast even if the number of Flyway migrations grows. However, you need a fair number of custom Gradle tasks to convert the Flyway migrations into a SQL dump at build time.

The performance numbers are indicative. They depend on your hardware and the specifics of your project, for example, the number of Flyway migrations.