模拟 Rest 模板返回 null 响应

Question

I am new to JUnit5 and Mockito framework in springboot. Here I am trying to mock the RestTemplate and return a 200 status with a string response. But I am getting a null response and the function throws a Null Pointer Exception. Is there any mistake in the way I am mocking the rest template?

Service

public class Abc {
  
  @Autowired
  RestTemplate template;

  @Value("${ser.url}")
  String url;

   void validate(String val){
       
       ResponseEntity<String> response;
       try{
            response = template.postForEntity(url, HTTP_ENTITY, String.class);

       } catch(Exception ex ){
             .....
       }     
        sysout(response); //Prints Null

        String res = response.getBody(); //Null Pointer exception
  }
}

Testing

class ServiceTest {

    @InjectMocks
    Abc abc; 

    @Mock
    RestTemplate template;

    @BeforeEach
    void setup(){
        MockitoAnnotations.init(this);
    }
 
    @Test
    void testIt(){
        when(template.postForEntity(anyString(), any(), ArgumentMatchers.<Class<String>>any())).
              thenReturn(new ResponseEntity<String>("value",HttpStatus.OK));
        
        abc.validate("abc"); 
    }
}

Answer 1

After long time experiments in the past I have realized that @InjectMocks sometimes works not as expected. So now I make use of @MockBean instead. This code works:

@Service    
public class Abc {
    @Autowired
    RestTemplate template;

    @Value("${ser.url}")
    String url;

    void validate(String val){

        ResponseEntity<String> response = null;
        try{
            response = template.postForEntity(url, new HttpEntity<>(""),
                    String.class);

        } catch(Exception ex ){
             ex.printStackTrace();
        }
        System.out.println(response); //Prints Null

        String res = response.getBody(); //Null Pointer exception
    }    
}

@SpringBootTest
class AbcTest {

    @Autowired
    Abc abc;

    @MockBean
    RestTemplate template;    

    @Test
    void testIt(){
        when(template.postForEntity(anyString(), any(), ArgumentMatchers.<Class<String>>any())).
                thenReturn(new ResponseEntity<String>("value", HttpStatus.OK));

        abc.validate("abc");
    }
}