Spring MongoDB 的单元测试返回 null

Question

I'm trying to Unit test my MongoDB-based Spring Boot application, and I'm getting a java.lang.NullPointerException: Cannot invoke "blueprint.model.Garage.getCarModel()" because "savedGarage" is null error. 代码如下：

我的服务：

 @Service
public class GarageService {

private final GarageRepository garageRepository;

@Autowired
public GarageService(GarageRepository garageRepository) {
    this.garageRepository = garageRepository;
}

public void addToGarage(Garage garage) {
    Optional<Garage> garageOptional = garageRepository.findByCarModel(garage.getCarModel());
    if(garageOptional.isPresent()) {
        throw new IllegalStateException("This Car model is already in our garage!");
    }
    garageRepository.save(garage);
}

public List<Garage> showOurGarage() {
    return garageRepository.findAll();
}

public void deleteFromGarage(String id) {
    boolean exists = garageRepository.existsById(id);
    if(!exists) {
        throw new IllegalStateException("A car with id " + id + " is not in our Garage.");
    }
    garageRepository.deleteById(id);
}

public void updateCar(String id, String carModel, Integer HP, Integer year, String designer) {
    Garage garage = garageRepository.findById(id)
            .orElseThrow(() -> new IllegalStateException(
                    "A car with the id " + id + " is not in our Garage."));
    if(carModel != null && carModel.length() > 0 && !Objects.equals(garage.getCarModel(), carModel)) {
        garage.setCarModel(carModel);
    }
    if(HP != null && !Objects.equals(garage.getHP(), HP)) {
        garage.setHP(HP);
    }
    if(year != null && !Objects.equals(garage.getYear(), year)) {
        garage.setYear(year);
    }
    if(designer != null && designer.length() > 0 && !Objects.equals(garage.getDesigner(), designer)) {
        garage.setDesigner(designer);
    }
    garageRepository.save(garage);
}
}

我的仓库：

@org.springframework.stereotype.Repository
public interface GarageRepository extends MongoRepository<Garage, String> {

Optional<Garage> findByCarModel(String carModel);

这是一个测试：

@DisplayName("Garage Service Test")
@DataMongoTest
class GarageServiceTest {

@Mock
private GarageRepository garageRepository;
private GarageService garageService;

@BeforeEach
void setUp() {
    MockitoAnnotations.openMocks(this);
    garageService = new GarageService(garageRepository);
}

@Test
@DisplayName("Add Car To Garage Test")
void testAddToGarage() {
    Garage testGarage = new Garage();
    testGarage.setId("630ca281f12905d5f5249f08");
    testGarage.setCarModel("Shelby Cobra");
    testGarage.setHP(485);
    testGarage.setYear(1965);
    testGarage.setDesigner("Carroll Shelby");

    Garage savedGarage = garageRepository.save(testGarage);

    String testedGarage = savedGarage.getCarModel();

    Optional<Garage> garages = garageRepository.findByCarModel("Shelby Cobra");
    assertEquals(testedGarage, garages.toString());
}

我对单元测试和 MongoDB 非常满意，所以我不确定这个错误发生在哪里以及为什么会发生。 我已经跳过添加 Controller 因为我认为代码的 rest 就足够了。

Answer 1

据我所见，garageRepository 被实例化为模拟，因此 save 方法根本不知道要返回什么，并默认返回 null 。 如果调用save()方法，您必须告诉 Mockito 返回什么。 这可以通过Mockito.when(...).thenReturn(...)来实现。

您的测试应该测试服务，但您不会调用服务的单个方法！

另一方面，查询存储库以获取已保存的 object 是没有意义的，因为 object 实际上没有保存（同样，存储库是一个模拟，您想测试服务，因此您要确保保存存储库的方法被正确调用）。 相反，您应该验证 save() 方法是否像

Mockito.verify(garageRepository).save(testGarage);

...或者如果由于现有 object 具有相同的 id 而出现异常。 尝试以下代码（未测试：）：

@DisplayName("Garage Service Test")
@DataMongoTest
class GarageServiceTest {

@Mock
private GarageRepository garageRepository;
private GarageService garageService;

@BeforeEach
void setUp() {
    MockitoAnnotations.openMocks(this);
    //This would be the way to make the mock return sth., 
    //but not really   needed
    //Garage returnObject = new Garage();
    //returnObject.setId("630ca281f12905d5f5249f08");
    //returnObject.set...(...);
    //Mockito.when(garageRepository.save(Mockito.ANY))
    //   .thenReturn(returnObject);
    garageService = new GarageService(garageRepository);
}

@Test
@DisplayName("Add Car To Garage Test")
//This is the 'positive test, object isn't persisted yet
void testAddToGarage() {
    Garage testGarage = new Garage();
    testGarage.setId("630ca281f12905d5f5249f08");
    testGarage.setCarModel("Shelby Cobra");
    testGarage.setHP(485);
    testGarage.setYear(1965);
    testGarage.setDesigner("Carroll Shelby");
    Mockito.when(garageRepository
    .findByCarModel(testGarage.getCarModel()))
    .thenReturn(Optional.empty());
    garageService.addToGarage(testGarage);
    Mockito.verify(garageRepository).save(testGarage);
}

@Test
@DisplayName("Add Car To Garage Test")
//This is the 'negative' test, the repository indicates that the object
//is already persisted
@Expected(IllegalStateException.class)
void testAddToGarageAlreadyPersisted() {
    Garage testGarage = new Garage();
    testGarage.setId("630ca281f12905d5f5249f08");
    testGarage.setCarModel("Shelby Cobra");
    testGarage.setHP(485);
    testGarage.setYear(1965);
    testGarage.setDesigner("Carroll Shelby");
    Mockito.when(garageRepository
    .findByCarModel(testGarage.getCarModel()))
    .thenReturn(Optional.of(testGarage));
    garageService.addToGarage(testGarage);
    Mockito.verify(garageRepository, Mockito.never()).save(testGarage);
}

}