模拟 s3Service + junit 时出现 NullPointerException

Question

我正在使用 amazon s3 进行文档存储。我需要为使用 s3.

的服务 class 编写测试用例

如何模拟 s3 对象？

我已经尝试了下面的方法，但是得到了 NPE。

示例测试用例：

@ExtendWith(MockitoExtension.class)
class MyServiceTest {

    @InjectMocks
    private MyService myService;

    @InjectMocks
    private S3Service s3Service;
    @Mock
    private S3Configuration.S3Storage s3Storage;
    @Mock
    private AmazonS3 amazonS3;

    @BeforeEach
    public void setup() {
        ReflectionTestUtils.setField(myService, "s3Service", s3Service);
        ReflectionTestUtils.setField(s3Service, "s3Storage", s3Storage);
    }

 @Test
    void getDetailTest() {

        given(s3Storage.getClient()).willReturn(amazonS3);
        given(s3Service.getBucket()).willReturn("BUCKET1");
        given(s3Service.readFromS3(s3Service.getBucket(),"myfile1.txt")).willReturn("hello from s3 file"); //Null pointer exception
}
}

下面是 s3 服务 class 抛出 NPE 的示例。

public String readFromS3(String bucketName, String key) {
        var s3object = s3Storage.getClient().getObject(new GetObjectRequest(bucketName, key));
//s3Object is getting null when run the test case.
    //more logic

}

如何从 MyService class 模拟 s3Service.readFromS3() ？

Answer 1

您不需要模拟测试中的每个对象，使用模拟来构建您的服务是非常好的...

@ExtendWith(MockitoExtension.class)
class MyServiceTest {

    private MyService myService;

    @Mock
    private AmazonS3 amazonS3;

    @BeforeEach
    public void setup() {
        this.myService = new MyService(amazonS3);
    }

    @Test
    void getDetailTest() {
        given(this.amazonS3.getXXX()).willReturn(new Yyyyy());
        assertEqual("ok", this.myService.doSmth());
    }
}

模拟 s3Service + junit 时出现 NullPointerException

NullPointerException while mocking s3Service + junit

java

junit

amazon-s3

mockito