To test a DAO class, for example, you will need to perform database queries that won't be persisted. For example, to test the DAO method to add a user, you want to make sure that the user is actually created in the database, but you don't want that test user to remain in the database. Transactions help you to do this with minimum effort.
Follow these steps to automatically revert the database modifications performed by a test method:
With TestNG, make the test class extend:
public class UserDAOTest extends AbstractTransactionalTestNGSpringContextTests {
...With JUnit, add the @Transactional annotation to the test class:
@Transactional
public class UserDAOTest {
...