JUnit testing native queries annotated with @Modifying

Question

I'm making a SpringBoot app where I have two classes with many-to-many relationship: User and Plant. I'm using a MySQL database, where I have tables users, plants and a joined table for the two classes user_plants.

I then have a UserRepository interface, where I defined a method for deleting entries from the user_plants table:

@Repository
public interface UserRepository extends JpaRepository<User, Integer> {

    @Modifying
    @Query(value = "DELETE FROM user_plants WHERE user_id = ?1 AND plant_id = ?2", nativeQuery = true)
    void deletePlantById(int userId, int plantId);
}

This method is later used in UserService class:

@Service
public class UserService {
  private final UserRepository userRepository;

   @Autowired
   public UserService(UserRepository userRepository){
       this.userRepository = userRepository;   }

   @Transactional
   public void deletePlant(int userId, int plantId){
       userRepository.deletePlantById(userId, plantId);
   }}

I have recently started learning about unit tests and I'm trying to write a unit test for UserRepository. I managed to successfully test all of the default JpaRepository methods, such as getById, findAll etc. However, the test for the method implemented by me always fails.

@DataJpaTest
@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
class UserRepositoryTest {

   @Autowired
   private UserRepository userRepository;
   private User user;

   @BeforeEach
   public void setUp(){
       Set<Plant> plantsSet = new LinkedHashSet<>();
       plantsSet.add(new Plant(5, "Monstera"));
       user = new User(1, "Alice", plantsSet);
       userRepository.save(user);
   }

   @AfterEach
   public void clean(){
       userRepository.deleteAll();
       user = null;
   }

   @Test
   void givenPlantIdAndUserIdShouldDeletePlantOfThatIdFromUserPlants() {
       userRepository.deletePlantById(1, 5);
       assertTrue(user.getOwnedPlants().isEmpty());
   }

I tested this method manually and I could see that it works correctly - changes to the database were made the way that I wanted. So why does the test fail? How should I go about writing it?