Repository tests verify your queries work correctly against a real database. Spring Boot’s @DataJpaTest starts a minimal slice — only JPA components — making tests fast while still catching real SQL issues. @DataJpaTest — What It Loads @DataJpaTest is a test slice annotation: @DataJpaTest class OrderRepositoryTest { // Spring loads: // - Your @Entity classes // - Your @Repository interfaces // - JPA infrastructure (EntityManager, transactions) // - An in-memory H2 database (by default) // // Spring does NOT load: // - @Service, @Controller, @Component classes // - Security configuration // - The full ApplicationContext } Each test method runs in a transaction that’s rolled back at the end — no data pollution between tests.