Java 如何在单个junit测试之前以编程方式设置h2数据库？

我有一个带有h2数据库的简单spring启动应用程序

我想编写单元测试，以确认我选择的注释的行为符合预期

我的代码如下：

import java.util.List;
import javax.persistence.*;
import lombok.*;
@NoArgsConstructor //otherwise there are errors on delete
@AllArgsConstructor
@RequiredArgsConstructor
@Entity
@Table(name = "pupils")
public class Pupil {
    
    @Id
    private long id;

    @NonNull
    private String name;
    
    @ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
    @JoinTable(
        name = "pupils_subjects", 
        joinColumns = @JoinColumn(name = "pupil_id"), 
        inverseJoinColumns = @JoinColumn(name = "subject_id"))
    @OrderColumn(name = "id")
    private List<Subject> subjects; 
}

我明白了

因此，我需要将设置放在不同的会话中。我该怎么做

import java.util.List;
import javax.persistence.*;
import lombok.*;

@NoArgsConstructor
@RequiredArgsConstructor
@Entity
@Table(name = "subjects")
public class Subject {

    @Id
    private long id;
    
    @NonNull
    private String name;
    
    @ManyToMany
    private List<Subject> subjects;

}

import org.springframework.data.repository.CrudRepository;

public interface PupilRepository extends CrudRepository<Pupil, Long> {}
public interface SubjectRepository extends CrudRepository<Subject, Long> {}

@ExtendWith(SpringExtension.class)
@DataJpaTest
public class BehaviourTest {

    @Autowired
    PupilRepository pupilRepo;
    
    @Autowired
    SubjectRepository subjectRepo;


    @Test
    public void testAddTwoSubjectsThenPupil() {
        //setup
        Subject math    = new Subject(0, "Maths");
        Subject english = new Subject(1, "English");
        subjectRepo.save(math);
        subjectRepo.save(english);

        //actual test
        math    = new Subject(0, "Maths");
        english = new Subject(1, "English");

        Pupil alice = new Pupil(0, "alice", Arrays.asList(math, english));
        pupilRepo.save(alice);
        assertThat(pupilRepo.count()).isEqualTo(1);
        assertThat(subjectRepo.count()).isEqualTo(2);
    }

org.springframework.dao.DataIntegrityViolationException: A different object with the same identifier value was already associated with the session : [com.example.petstore.stacko.jpa0.Subject#1]; nested exception is javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [com.example.petstore.stacko.jpa0.Subject#1]
    at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:400)
...