Spring Rest Template mocking with Spock

Question

Can anyone show me an example, how to test RestTemplate using Spock. My classes looks like this:

@Service
public class SomeService {

    @Autowired
    private EndpointUrlProvider endpointUrlProvider;
    private RestTemplate restTemplate = new RestTemplate();

    public SomeResponse doSomePostRequest(HttpEntity<?> httpEntity) throws Exception {
    ResponseEntity<SomeResponse> response;
            try{
                response = restTemplate.postForEntity(endpointUrlProvider.getSomeUrl(),httpEntity,SomeResponse.class);
            } catch (Exception e){
                throw new Exception("Exception occured during post for:" + httpEntity.getBody().getClass().getSimpleName() + " Cause: " + e.getMessage());
            }
            if(response.getStatusCode() == HttpStatus.OK){
                return response.getBody();
            }
            throw new Exception("Error during " + response.getBody().getClass().getSimpleName() + "Http status is diffrent than 200: " + response.getBody().toString());
        }
    }

Tests:

class SomeTest extends Specification {

    RestTemplate restTemplate = Mock {
        postForEntity(_, _, SomeResponse.class) >> new ResponseEntity(new SomeResponse(), HttpStatus.OK)
    }

    @Autowired
    SomeService someService

    def "someTest"() {
        when:
        SomeResponse someResponse = someService.doSomePostRequest(new HttpEntity<>(new SomeBody(), new HttpHeaders()))
        then:
        someResponse == new SomeResponse()
    }
}

The major problem is mocking behaviour of RestTemplate,I looking for solution how to do it in proper way. I'm dont use spring boot.

Answer 1

The situation is following:

You create new RestTemplate in your service class.

  private RestTemplate restTemplate = new RestTemplate();

Then you create mock in tests and call your service method:

    RestTemplate restTemplate = Mock {
            postForEntity(_, _, SomeResponse.class) >> new ResponseEntity(new SomeResponse(), HttpStatus.OK)
        }
                  ....
    someService.doSomePostRequest

But your service still has usual rest template inside. You should inject mock object. I would suggest you doing it through constructor. So change your code to:

@Service
public class SomeService {

private EndpointUrlProvider endpointUrlProvider;
private RestTemplate restTemplate;

@Autowired
public SomeService(EndpointUrlProvider endpointUrlProvider, RestTemplate restTemplate){
  this.endpointUrlProvider = endpointUrlProvider;
  this.restTemplate = restTemplate;
}

And your test will be:

class SomeTest extends Specification {

    RestTemplate restTemplate = Mock {
        postForEntity(_, _, SomeResponse.class) >> new ResponseEntity(new SomeResponse(), HttpStatus.OK)
    }

    SomeService someService = new SomeService (  null, restTemplate);

    def "someTest"() {
        when:
        SomeResponse someResponse = someService.doSomePostRequest(new HttpEntity<>(new SomeBody(), new HttpHeaders()))
        then:
        someResponse == new SomeResponse()
    }
}

Now your service object will call method on injected MOCK, not usual RestTemplate

ps

Constructor injection considered to be a good practice by spring.

It's better to create a RestTemplate bean and inject it everywhere, than create new object in all services.