Java:为什么这个单元测试不起作用(一对多关系)?

我有以下与java单元测试相关的代码

    @Test
    public void testFindPetsByOwner() {
        CustomerDTO customerDTO = createCustomerDTO();
        CustomerDTO newCustomer = userController.saveCustomer(customerDTO);

        PetDTO petDTO = createPetDTO();
        petDTO.setOwnerId(newCustomer.getId());
        PetDTO newPet = petController.savePet(petDTO);
        petDTO.setType(PetType.DOG);
        petDTO.setName("DogName");
        PetDTO newPet2 = petController.savePet(petDTO);

        List<PetDTO> pets = petController.getPetsByOwner(newCustomer.getId());
        Assertions.assertEquals(pets.size(), 2);
        Assertions.assertEquals(pets.get(0).getOwnerId(), newCustomer.getId());
        Assertions.assertEquals(pets.get(0).getId(), newPet.getId());
    }

最后一次assert.equals的结果失败,如下所示

org.opentest4j.AssertionFailedError: 
Expected :1
Actual   :2
<Click to see difference>

PetController.java

    @PostMapping
    public PetDTO savePet(@RequestBody PetDTO petDTO) {

        Pet newPet = new Pet();
        BeanUtils.copyProperties(petDTO, newPet, "id");
        Pet savedPet = petService.save(newPet);
        BeanUtils.copyProperties(savedPet, petDTO);
        return petDTO;
    }

    @GetMapping("/owner/{ownerId}")
    public List<PetDTO> getPetsByOwner(@PathVariable long ownerId) {

        List<Pet> petsByOwner = petService.getPetsByOwner(ownerId);
        List<PetDTO> petDTOList = new ArrayList<>();
        for(Pet pet:petsByOwner){
            PetDTO petDTO = new PetDTO();
            BeanUtils.copyProperties(pet, petDTO);
            petDTOList.add(petDTO);
        }
        return petDTOList;
    }

PetService.java

    public Pet save(Pet pet){

        Customer customer = customerRepository.findById(pet.getOwnerId()).orElseThrow(() -> new CustomerNotFoundException());

        pet.setCustomer(customer);
        customer.getPets().add(pet);
        customerRepository.save(customer);
        List<Pet> savedPets =  customer.getPets();
        Pet nPet =  savedPets.get(savedPets.size() - 1 );
        return nPet;
    }

    public List<Pet> getPetsByOwner(long ownerId) {
        return petRepository.findByOwnerId(ownerId);
    }

PetDTO.java

public class PetDTO {
    private long id;
    private PetType type;
    private String name;
    private long ownerId;
    private LocalDate birthDate;
    private String notes;
// getters and setters
}

Pet.java

@Entity
public class Pet {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private long id;

    @NotNull
    @Enumerated(EnumType.STRING)
    private PetType type;

    private String name;
    
    private long ownerId;

    private LocalDate birthDate;

    private String notes;

    @ManyToMany(mappedBy = "pets")
    private List<Schedule> schedules;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "customer_id")
    private Customer customer;
//getters and setters
}

客户.java

@Entity
public class Customer extends Person {

    private String phoneNumber;

    private String notes;
    
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "customer", cascade = CascadeType.ALL )
    private List<Pet> pets = new ArrayList<>();
//getters and setters
}

Person.java

@MappedSuperclass
public class Person {

    @Id
    // watch out if this generation strategy becomes a bug later
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    protected long id;
    @Nationalized
    private String name;
...
}

PetRepository.java

@Repository
public interface PetRepository extends JpaRepository<Pet, Long> {

    List<Pet> findByOwnerId(long ownerId);
    
}

下面可以看到与该bug相关的类。我怀疑这个错误可能与单元测试中的传递引用有关。 注意:我已经编辑了帖子,添加了其中一位投稿人要求的相关课程