title: Testing using Wiremock to test a Feign Client
body: <p>So I've spent a good day trying to figure this out and it's been quite difficult. 
  So the issue is that when you have a simple client using Feign as below:</p>
  
  <pre><code>@FeignClient(name = "identity-service")
  public interface IdentityClient {
  
      @GetMapping(value = "/")
      String request();
  }
  </code></pre>
  
  <p>And of course your application is annotated with the <code>@EnableFeignClients</code> as below:</p>
  
  <pre><code>@EnableEurekaClient
  @SpringBootApplication
  @EnableFeignClients
  public class LicenseServiceApplication {
  
      public static void main(String[] args) {
          SpringApplication.run(LicenseServiceApplication.class, args);
      }
  }
  </code></pre>
  
  <p>If I have a test for that feign client as below:</p>
  
  <pre><code>@RunWith(SpringRunner.class)
  @SpringBootTest(webEnvironment= SpringBootTest.WebEnvironment.NONE)
  public class LicenseServiceTest {
  
      @ClassRule
      public static WireMockClassRule wiremock = new WireMockClassRule(
          WireMockSpring.options().dynamicPort());
  
      // A service that calls out over HTTP
      @Autowired
      private IdentityClient identityClient;
  
      // Using the WireMock APIs in the normal way:
      @Test
      public void contextLoads() throws Exception {
          stubFor(get(urlEqualTo("/"))
              .willReturn(aResponse().withHeader("Content-Type", 
                       "text/plain").withBody("Hello World!")));
      // We're asserting if WireMock responded properly
      assertThat(this.identityClient.request()).isEqualTo("Hello World!");
      }
  
  }
  </code></pre>
  
  <p>It generates the following stacktrace:</p>
  
  <pre><code>java.lang.RuntimeException: com.netflix.client.ClientException: Load balancer does not have available server for client: identity-service
  
      at org.springframework.cloud.netflix.feign.ribbon.LoadBalancerFeignClient.execute(LoadBalancerFeignClient.java:71)
      at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:97)
      at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:76)
      at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103)
      at com.sun.proxy.$Proxy122.request(Unknown Source)
      at com.gov.zw.service.LicenseServiceTest.contextLoads(LicenseServiceTest.java:34)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
      at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
      at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
      at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
      at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
      at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
      at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
      at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
      at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)
      at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
      at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
      at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
      at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
      at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
      at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
      at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
      at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
      at com.github.tomakehurst.wiremock.junit.WireMockClassRule$1.evaluate(WireMockClassRule.java:70)
      at org.junit.rules.RunRules.evaluate(RunRules.java:20)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
      at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
      at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
      at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
      at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
      at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
      at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
  Caused by: com.netflix.client.ClientException: Load balancer does not have available server for client: identity-service
      at com.netflix.loadbalancer.LoadBalancerContext.getServerFromLoadBalancer(LoadBalancerContext.java:483)
      at com.netflix.loadbalancer.reactive.LoadBalancerCommand$1.call(LoadBalancerCommand.java:184)
      at com.netflix.loadbalancer.reactive.LoadBalancerCommand$1.call(LoadBalancerCommand.java:180)
      at rx.Observable.unsafeSubscribe(Observable.java:10211)
      at rx.internal.operators.OnSubscribeConcatMap.call(OnSubscribeConcatMap.java:94)
      at rx.internal.operators.OnSubscribeConcatMap.call(OnSubscribeConcatMap.java:42)
      at rx.Observable.unsafeSubscribe(Observable.java:10211)
      at rx.internal.operators.OperatorRetryWithPredicate$SourceSubscriber$1.call(OperatorRetryWithPredicate.java:127)
      at rx.internal.schedulers.TrampolineScheduler$InnerCurrentThreadScheduler.enqueue(TrampolineScheduler.java:73)
      at rx.internal.schedulers.TrampolineScheduler$InnerCurrentThreadScheduler.schedule(TrampolineScheduler.java:52)
      at rx.internal.operators.OperatorRetryWithPredicate$SourceSubscriber.onNext(OperatorRetryWithPredicate.java:79)
      at rx.internal.operators.OperatorRetryWithPredicate$SourceSubscriber.onNext(OperatorRetryWithPredicate.java:45)
      at rx.internal.util.ScalarSynchronousObservable$WeakSingleProducer.request(ScalarSynchronousObservable.java:276)
      at rx.Subscriber.setProducer(Subscriber.java:209)
      at rx.internal.util.ScalarSynchronousObservable$JustOnSubscribe.call(ScalarSynchronousObservable.java:138)
      at rx.internal.util.ScalarSynchronousObservable$JustOnSubscribe.call(ScalarSynchronousObservable.java:129)
      at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)
      at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)
      at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)
      at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)
      at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:48)
      at rx.internal.operators.OnSubscribeLift.call(OnSubscribeLift.java:30)
      at rx.Observable.subscribe(Observable.java:10307)
      at rx.Observable.subscribe(Observable.java:10274)
      at rx.observables.BlockingObservable.blockForSingle(BlockingObservable.java:445)
      at rx.observables.BlockingObservable.single(BlockingObservable.java:342)
      at com.netflix.client.AbstractLoadBalancerAwareClient.executeWithLoadBalancer(AbstractLoadBalancerAwareClient.java:117)
      at org.springframework.cloud.netflix.feign.ribbon.LoadBalancerFeignClient.execute(LoadBalancerFeignClient.java:63)
      ... 35 more
  </code></pre>
  
  <p>Also do bear in mind I was following the Spring Cloud Contract WireMock documentation <a href="https://cloud.spring.io/spring-cloud-contract/multi/multi__spring_cloud_contract_wiremock.html" rel="nofollow noreferrer">here</a> and I looked through their Github examples <a href="https://github.com/spring-cloud/spring-cloud-contract/tree/master/samples" rel="nofollow noreferrer">here</a>. But the results are common in that most tests or implementations are using <code>RestTemplate</code> rather than <code>Feign</code>.</p>