How to unit test hystrix fallback with spring-cloud - spring-cloud

Question

I've implemented an http call with feign and hystrix following the following article : https://blog.crafties.fr/2017/07/23/setup-a-circuit-breaker-with-hystrix/
I'm using those dependencies :
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-openfeign</artifactId>
<version>2.0.0.M1</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-netflix</artifactId>
<version>2.0.0.M7</version>
<type>pom</type>
<scope>import</scope>
</dependency>
My implementation looks like this :
#FeignClient(name = "someName",
url = "https://my.url/to/service", fallbackFactory = RTKClientFallbackFactory.class)
public interface RTKClient {
#PostMapping(value = "/v1/topics/rt/messages")
KRestProducerResponse sendT(#RequestBody T t);
}
#Component
public class RTKClientFallbackFactory implements FallbackFactory<RTKClient>{
#Override
public RTKClient create(Throwable cause) {
return new RTKClientFallback(cause);
}
}
public class RTKClientFallback implements RTKClient{
private final Throwable cause;
private final static Logger LOG = LogManager.getLogger(RTKClientFallback.class);
public RTKClientFallback(Throwable cause) {
this.cause = cause;
}
#Override
public KRestProducerResponse sendTemplate(T t) {
KRestProducerResponse response = new KRestProducerResponse();
if (cause instanceof FeignException) {
response.setStatus(((FeignException)cause).status());
}
return response;
}
}
This works when I test it manually.
The issue for me is to unit test the fallback
This is how I tried :
#RunWith(SpringRunner.class)
#SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
#AutoConfigureWireMock(port = 0)
#EnableCircuitBreaker
#EnableFeignClients
public class RTKClientFallbackTest {
#Autowired
public RTKClient client;
#Rule
public WireMockRule wireMockRule = new WireMockRule(8089);
#Test
public void should_fall_back_with_error_code_in_response() {
stubFor(get(urlEqualTo("https://my.url/to/service/v1/topics/rt/messages"))
.willReturn(aResponse().withStatus(404)));
T t = new T();
KRestProducerResponse response = client.sendTemplate(t);
assertEquals(404, response.getStatus());
}
}
What i don't understand is the following things :
How to link my stub and my FeignClient ? (as of now, my test calls the real endpoint)
How can I enable hystrix in this context (If I make it fail my messing up the url, I see it's not using the fallback)
Any ideas are welcome.
Thank you