Mockito：如何模拟注入对象没有no-arg构造函数的spring特殊DI

Question

我在单元测试中使用Mockito 3.4.6，实际上，我已经将Mockito集成到我的单元测试中，它工作得很好。虽然，现在我需要优化一些单元测试，这是一个特殊的依赖注入，注入的对象没有no-arg构造函数，我尝试了@spy，但它不起作用。

@injectmocks Mockito将尝试只通过构造函数注入、setter注入或属性注入来注入mocks，顺序如下所述。

另外，如果只使用@spy，它将抛出MockitoException:

org.mockito.exceptions.base.MockitoException: 
Failed to release mocks

This should not happen unless you are using a third-part mock maker

...
Caused by: org.mockito.exceptions.base.MockitoException: Unable to initialize @Spy annotated field 'api'.
Please ensure that the type 'DtInsightApi' has a no-arg constructor.
...
Caused by: org.mockito.exceptions.base.MockitoException: Please ensure that the type 'DtInsightApi' has a no-arg constructor.

请参见下面的伪代码：

@Configuration
public class SdkConfig {

    @Resource
    private EnvironmentContext environmentContext;

    @Bean(name = "api")
    public DtInsightApi getApi() {
     
        DtInsightApi.ApiBuilder builder = new DtInsightApi.ApiBuilder()
                    .setServerUrls("sdkUrls")
        return builder.buildApi();
    }
}

public class DtInsightApi {
    private String[] serverUrls;

    DtInsightApi(String[] serverUrls) {
        this.serverUrls = serverUrls;
    }
    
    // inner class
    public static class ApiBuilder {
        String[] serverUrls;

        public ApiBuilder() {
        }
        ...code...

        public DtInsightApi buildApi() {
           return new DtInsightApi(this.serverUrls);
        }
    }

    ...code...

}

public Test{
   
   @Autowired
   private PendingTestService service;

   @Spy
   private Api api = getDtInsightApi();

   @Mock
   private MockService mockService;

   @Before
    public void setUp() throws Exception {
        // open mock
        MockitoAnnotations.openMocks(this);
        // i use doReturn(...).when() for @Spy object
        Mockito.doReturn(mockService).when(api)
                   .getSlbApiClient(MockService.class);
        Mockito.when(mockService.addOrUpdate(any(MockDTO.class)))
                   .thenReturn(BaseObject.getApiResponseWithSuccess());
    }

    public DtInsightApi getDtInsightApi () {
        return new DtInsightApi.ApiBuilder()
                .setServerUrls(new String[]{"localhost:8080"})
                .buildApi();
    }

    @Test
    public void testUpdate() {
        service.update();
    }
}

@Service
public class PendingTestService{
   
   @Autowired
   DtInsightApi api;

   public void update() {
      // here mockService isn't the object i mocked
      MockService mockService = api.getSlbApiClient(MockService.class);
      mockService.update();
   }
}

问题：如何模拟没有no-arg构造函数的DI对象DtInsightApi。

Answer 1

public class Test{
    @MockBean
    @Qualifier("api")
    private DtInsightApi api;

   @Mock
   private MockService mockService;

    @Before
    public void setUp() throws Exception {
        // open mock
        MockitoAnnotations.openMocks(this);
        BDDMockito.given(this.api.getSlbApiClient(MockService.class)).willReturn(mockService);
    }

    @Autowired
    private PendingTestService service;


    @Test
    public void testUpdate() {
        service.update();
    }
}

调试mockService您可以看到mockService实例是由mockito、mock success生成的。

您还可以参考Spring docs示例：单元测试中的mockRemoteService。

import org.junit.*;
import org.junit.runner.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.context.*;
import org.springframework.boot.test.mock.mockito.*;
import org.springframework.test.context.junit4.*;

import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;

@RunWith(SpringRunner.class)
@SpringBootTest
public class MyTests {

    @MockBean
    private RemoteService remoteService;

    @Autowired
    private Reverser reverser;

    @Test
    public void exampleTest() {
        // RemoteService has been injected into the reverser bean
        given(this.remoteService.someCall()).willReturn("mock");
        String reverse = reverser.reverseSomeCall();
        assertThat(reverse).isEqualTo("kcom");
    }

}