如何测试更新方法?

I am new in unit testing and use JUnit in my Java (Spring Boot) app. I sometimes need to test update methods, but when I search on the web, there is not a proper example or suggestion. So, could you please clarify me how to test the following update method? I think this may require a different approach than testing void. I also thought that while testing first mocking the record and then update its field and then update. Finally retrieve the record again and compare the updated properties. But I think there may be more proper approach than this inexperienced one.

public PriceDTO update(UUID priceUuid, PriceRequest request) {
    Price price = priceRepository
                    .findByUuid(priceUuid)
                    .orElseThrow(() -> new EntityNotFoundException(PRICE));

    mapRequestToEntity(request, price);
    Price updated = priceRepository.saveAndFlush(price);
    
    return new PriceDTO(updated);
}

private void mapRequestToEntity(PriceRequest request, Price entity) {
    entity.setPriceAmount(request.getPriceAmount());
    // set other props
}

推荐答案

您需要按照以下方式做一些事情:

public class ServiceTest {

    @Mock
    private PriceRepository priceRepository;

    (...)

    @Test
    public void shouldUpdatePrice() throws Exception {
        // Arrange
        UUID priceUuid = // build the Price UUID
        PriceRequest priceUpdateRequest = // build the Price update request
        Price originalPrice = // build the original Price  
        doReturn(originalPrice).when(this.priceRepository).findByUuid(isA(UUID.class));
        doAnswer(AdditionalAnswers.returnsFirstArg()).when(this.priceRepository).saveAndFlush(isA(Price.class));

        // Act
        PriceDTO updatedPrice = this.service.update(priceUuid, priceUpdateRequest);

        // Assert
        // here you need to assert that updatedPrice is as you expect according to originalPrice and priceUpdateRequest
    }
}