Junit Test case Spring boot controller returning null value in ResponseEntity

Question

In my project I am creating a rest endpoint which is responsible to consume grpc service response. Now I want to write testcase for the controller class but the Junit test cases returning me null null values.

MyController.java

@RestController
@RequestMapping("/v1")
public class MyController {
    @Autowired
    private MyConsumerService consumer;

    public MyController(MyConsumerService consumer) {
        this.consumer=consumer;   
    }
     
    @GetMapping("/data")
    public ResponseEntity<Records> getData(@RequestParam("data") String data) {
        Records records = consumer.getGrpcResponse(data);
        return new ResponseEntity<>(Records, HttpStatus.OK);
    }
}

MyConsumerServiceImpl.java:

public class MyConsumerServiceImpl implements MyConsumerService {
    @GrpcClient("user-grpc-service")
    private userGrpc.userBlockingStub stub;

    @Override
    public Records getGrpcResponse(data) {
        Records records = new Records();
        UserRequest request = UserRequest.newBuilder()
            .setUserName(data)
            .build();
        APIResponse response = stub.userRequest(request);
        records.setUserName(response.getUserName());
        return records;
   }
}

MyControllerTest.java:

@ExtendWith(MockitoExtension.class)
public class MyControllerTest {
    private MyConsumerService mockerService;
    private MyController controller;

    @BeforeEach
    void setup(){
        mockerService = mock(MyConsumerService.class);
        controller = new MyController(mockerService);
    }

    @Test
    public void shouldGet(){
        final var data="Hello";
        when(mockerService.getGrpcResponse(data)).thenReturn(new Records());
        final var responseEntity=controller.getData(data);
        assertEquals(responseEntity.getBody(),new Records());
    }
}

responseEntity.getBody() is returning null .

Normal flow is working fine but with Junit when I am mocking the client service call, it is returning null .

I am confused why always it is returning null . Any idea where I am getting wrong.

Answer 1

you have not added when then statement for service.getData(), and below stubbing have not been called any where

when(mockerService.getGrpcResponse(data)).thenReturn(new Records());

use when then to mock service.getData() like this,

when(mockerService.getData(data)).thenReturn(new Records());

Answer 2

annotate this 'MyControllerTest' class with @WebMvcTest(MyController.class) and the rerun it will work, otherwise its not able to mock actual controller class.