Service Layer Testing

• It’s NOT a target for slice testing because it’s already covered by unit tests
  • the service layer is where your core business logic lives
  • use unit tests for the service layer < they’re much more effective & use tools like JUnit 5 and Mockito
• Add @Transactional on top of the testing class (ex. UserServiceTest.java) → When you test a service method that uses a repository to change data in the database