[Unit testing Java] Unit testing Junit Controller

Controller:

@RestController
@RequestMapping(path = "/ratings")
public class RatingController {
    private static final Logger LOGGER = LoggerFactory.getLogger(RatingController.class);
    private TourRatingService tourRatingService;

    private RatingAssembler assembler;

    @Autowired
    public RatingController(TourRatingService tourRatingService, RatingAssembler assembler) {
        this.tourRatingService = tourRatingService;
        this.assembler = assembler;
    }

    @GetMapping
    public List<RatingDto> getAll() {
        LOGGER.info("GET /ratings");
        return assembler.toResources(tourRatingService.lookupAll());
    }

    @GetMapping("/{id}")
    public RatingDto getRating(@PathVariable("id") Integer id) {
        LOGGER.info("GET /ratings/{id}", id);
        return assembler.toResource(tourRatingService.lookupRatingById(id)
                .orElseThrow(() -> new NoSuchElementException("Rating " + id + " not found"))
        );
    }


    /**
     * Exception handler if NoSuchElementException is thrown in this Controller
     *
     * @param ex exception
     * @return Error message String.
     */
    @ResponseStatus(HttpStatus.NOT_FOUND)
    @ExceptionHandler(NoSuchElementException.class)
    public String return400(NoSuchElementException ex) {
        LOGGER.error("Unable to complete transaction", ex);
        return ex.getMessage();
    }
}

We don't want to use real TourRatingService, we want to inject mock service.

/**
 * Invoke the Controller methods via HTTP.
 * Do not invoke the tourRatingService methods, use Mock instead
 */
@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = RANDOM_PORT)
public class RatingControllerTest {
    private static final String RATINGS_URL = "/ratings";

    //These Tour and rating id's do not already exist in the db
    private static final int TOUR_ID = 999;
    private static final int RATING_ID = 555;
    private static final int CUSTOMER_ID = 1000;
    private static final int SCORE = 3;
    private static final String COMMENT = "comment";

    @MockBean
    private TourRatingService tourRatingServiceMock;

    @Mock
    private TourRating tourRatingMock;

    @Mock
    private Tour tourMock;

    @Autowired
    private TestRestTemplate restTemplate;


    @Before
    public void setupReturnValuesOfMockMethods() {
        when(tourRatingMock.getTour()).thenReturn(tourMock);
        when(tourMock.getId()).thenReturn(TOUR_ID);
        when(tourRatingMock.getComment()).thenReturn(COMMENT);
        when(tourRatingMock.getScore()).thenReturn(SCORE);
        when(tourRatingMock.getCustomerId()).thenReturn(CUSTOMER_ID);
    }


    /**
     *  HTTP GET /ratings
     */
    @Test
    public void getRatings() {
        when(tourRatingServiceMock.lookupAll()).thenReturn(Arrays.asList(tourRatingMock, tourRatingMock, tourRatingMock));

        ResponseEntity<List<RatingDto>> response = restTemplate.exchange(RATINGS_URL, HttpMethod.GET,null,
                                                    new ParameterizedTypeReference<List<RatingDto>>() {});

        assertThat(response.getStatusCode(), is(HttpStatus.OK));
        assertThat(response.getBody().size(), is(3));
    }

    /**
     *  HTTP GET /ratings/{id}
     */
    @Test
    public void getOne()  {

        when(tourRatingServiceMock.lookupRatingById(RATING_ID)).thenReturn(Optional.of(tourRatingMock));

        ResponseEntity<RatingDto> response =
                restTemplate.getForEntity(RATINGS_URL + "/" + RATING_ID, RatingDto.class);

        assertThat(response.getStatusCode(), is(HttpStatus.OK));
        assertThat(response.getBody().getCustomerId(), is(CUSTOMER_ID));
        assertThat(response.getBody().getComment(), is(COMMENT));
        assertThat(response.getBody().getScore(), is(SCORE));
    }

https://github.com/zhentian-wan/spring-path/tree/master/explorecali/src/test/java/com/example/ec