mock resttemplate to test a service as restFul client

I have a service class, written in spring, with some methods.

One of this acts as a restful consumer like below:

HttpEntity request = new HttpEntity<>(getHeadersForRequest());
RestTemplate restTemplate = new RestTemplate();
String url = ENDPOINT_URL.concat(ENDPOINT_API1);

UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl(url)
                                        .queryParam("param1", parameter1);
ReportModel infoModel = null;
try {
    infoModel = restTemplate.exchange(builder.toUriString(),
                    HttpMethod.GET, request, ReportModel.class).getBody();
} catch (HttpClientErrorException | HttpServerErrorException e){
    e.printStackTrace();
}

I want to use Mockito to mock my service, but every method that interacts with restful server instance a new RestTemplate.

I’ve to create a static class to Inject it into my service?

Answer

One of the benefits from dependency injection is to be able to easily mock your dependencies. In your case it would be a lot easier to create a RestTemplate bean:

@Bean
public RestTemplate restTemplate() {
    return new RestTemplate();
}

And in stead of using new RestTemplate() in your client you should use:

@Autowired
private RestTemplate restTemplate;

For the unit testing with Mockito you’ll have to mock the RestTemplate, for example by using:

@RunWith(MockitoJUnitRunner.class)
public class ClientTest {
    @InjectMocks
    private Client client;
    @Mock
    private RestTemplate restTemplate;
}

In this case Mockito will mock and inject the RestTemplate bean in your Client. If you don’t like mocking and injecting through reflection you can always go for a separate constructor or setter to inject the RestTemplate mock.

Now you can write a test like this:

client.doStuff();
verify(restTemplate).exchange(anyString(), eq(HttpMethod.GET), any(HttpModel.class), eq(ReportModel.class));

You’ll probably want to test more than that, but it gives you a basic idea.