[FIXED] Springboot test issue: Mockito is returning empty object

Issue

I am trying to build a prototype that is using gradle as build tool and openjdk-11. This prototype will build a rest-api on springboot framework.

My module is working fine with rest-api call and returning expected result. However, as I am now trying to write a test for the rest api, the test is failing as Mockito is returning empty object. Would appreciate any insight on how should I write a test for this rest-api or what to do to fix it.

My controller:

@RestController
public class GreetingController {

private static final String template = "Hello, %s!";
private final AtomicLong counter = new AtomicLong();

@Autowired
GreetingService service;

@RequestMapping("/greeting")
public Greeting greeting(@RequestParam(value="name", defaultValue="World") String name) {
    return service.getGreetings(0L, String.format(template, name));
}
}

The service:

@Service
public class GreetingService {

public Greeting getGreetings() {
    return new Greeting(1L, "Hello World");
}

public Greeting getGreetings(Long id, String name) {
    return new Greeting(id, name);
}
}

The Model:

@Builder
@Data
@RequiredArgsConstructor
@JsonDeserialize(builder = Greeting.class)
public class Greeting {
    @NonNull
    private Long id;

    @NonNull
    private String content;

}

The main class:

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

I executed this by :

gradle bootrun

And then from browser, tried :

http://localhost:8080/greeting 

And that returned:

{"id":0,"content":"Hello, World!"}

Again tried:

http://localhost:8080/greeting?name=Patty

and that returned:

{"id":0,"content":"Hello, Patty!"}

Now, I was trying to write test to validate api calls similar to the above calls programatically. So I tried:

@RunWith(MockitoJUnitRunner.class)
public class GreetingControllerTest {

    private MockMvc mockMvc;

    @Mock
    private GreetingService service;

    @InjectMocks
    private GreetingController controller


    @Test
    public void testGreeting() throws Exception {

        Greeting  greeting  = new Greeting(0L,"Patty!");
        String expectedResponse  = "{\"id\":0,\"content\":\"Hello, Patty!\"}";


        //JacksonTester.initFields(this, new ObjectMapper());
        mockMvc = MockMvcBuilders.standaloneSetup(controller)
                .build();
        Mockito.when(service.getGreetings(0L,"Patty")).thenReturn(greeting);


        MockHttpServletResponse response = mockMvc
                .perform(get("/greeting?name=Patty")
                        .contentType(MediaType.ALL))
                .andReturn()
                .getResponse();


        assertThat(response.getStatus()).isEqualTo(HttpStatus.OK.value());
        assertThat(response.getContentAsString()).isEqualTo(expectedResponse)


    }




}

The error msg is :

org.junit.ComparisonFailure: 
Expected :"{"id":0,"content":"Hello, Patty!"}"
Actual   :""

Failing from this line:

assertThat(response.getContentAsString()).isEqualTo(expectedResponse)

Thanks in advance.

Solution

This helped me understanding: Mockito - thenReturn always returns null object

I changed the Mockito.when part to :

Mockito.when(service.getGreetings(Mockito.anyLong(),Mockito.anyString())).thenReturn(greeting);

and it worked

Answered By - VictorGram