How to Integration Test spring-cloud-netflix & Feign, using WireMock

Question

I use Spring-Cloud-Netflix for communication between micro services. Let's say I have two services, Foo and Bar, and Foo consumes one of Bar's REST endpoints. I use an interface annotated with @FeignClient:

@FeignClient
public interface BarClient {
  @RequestMapping(value = "/some/url", method = "POST")
  void bazzle(@RequestBody BazzleRequest);
}

Then I have a service class SomeService in Foo, which calls the BarClient.

@Component
public class SomeService {
    @Autowired
    BarClient barClient;

    public String doSomething() {
      try {
        barClient.bazzle(new BazzleRequest(...));
        return "so bazzle my eyes dazzle";
      } catch(FeignException e) {
        return "Not bazzle today!";
      }

    }
}

Now, to make sure the communication between services works, I want to build a test that fires a real HTTP request against a fake Bar server, using WireMock. The test should make sure that feign correctly decodes the service response and reports it to SomeService.

public class SomeServiceIntegrationTest {

    @Autowired SomeService someService;

    @Test
    public void shouldSucceed() {
      stubFor(get(urlEqualTo("/some/url"))
        .willReturn(aResponse()
            .withStatus(204);

      String result = someService.doSomething();

      assertThat(result, is("so bazzle my eyes dazzle"));
    }

    @Test
    public void shouldFail() {
      stubFor(get(urlEqualTo("/some/url"))
        .willReturn(aResponse()
            .withStatus(404);

      String result = someService.doSomething();

      assertThat(result, is("Not bazzle today!"));
    }
}

How can I successfully inject such a WireMock server into Eureka, so that Feign is able to find it and communicate with it?

Answer 1

Here is an example of using WireMock to test SpringBoot configuration with Feign client and Hystrix fallback.

If you are using Eureka as a server discovery, you need to disable it by setting a property "eureka.client.enabled=false".

First, we need to enable the Feign/Hystrix configuration for our application:

@SpringBootApplication
@EnableFeignClients
@EnableCircuitBreaker
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

@FeignClient(
        name = "bookstore-server",
        fallback = BookClientFallback.class,
        qualifier = "bookClient"
)
public interface BookClient {

    @RequestMapping(method = RequestMethod.GET, path = "/book/{id}")
    Book findById(@PathVariable("id") String id);
}

@Component
public class BookClientFallback implements BookClient {

    @Override
    public Book findById(String id) {
        return Book.builder().id("fallback-id").title("default").isbn("default").build();
    }
}

Please note that we are specifying a fallback class for the Feign client. Fallback class will be called every time Feign client call fails (e.g. connection timeout).

In order for tests to work, we need to configure the Ribbon loadbalancer (will be used internally by Feign client when sending http request):

@RunWith(SpringRunner.class)
@SpringBootTest(properties = {
        "feign.hystrix.enabled=true"
})
@ContextConfiguration(classes = {BookClientTest.LocalRibbonClientConfiguration.class})
public class BookClientTest {

    @Autowired
    public BookClient bookClient;

    @ClassRule
    public static WireMockClassRule wiremock = new WireMockClassRule(
            wireMockConfig().dynamicPort()));

    @Before
    public void setup() throws IOException {
        stubFor(get(urlEqualTo("/book/12345"))
                .willReturn(aResponse()
                        .withStatus(HttpStatus.OK.value())
                        .withHeader("Content-Type", MediaType.APPLICATION_JSON)
                        .withBody(StreamUtils.copyToString(getClass().getClassLoader().getResourceAsStream("fixtures/book.json"), Charset.defaultCharset()))));
    }

    @Test
    public void testFindById() {
        Book result = bookClient.findById("12345");

        assertNotNull("should not be null", result);
        assertThat(result.getId(), is("12345"));
    }

    @Test
    public void testFindByIdFallback() {
        stubFor(get(urlEqualTo("/book/12345"))
                .willReturn(aResponse().withFixedDelay(60000)));

        Book result = bookClient.findById("12345");

        assertNotNull("should not be null", result);
        assertThat(result.getId(), is("fallback-id"));
    }

    @TestConfiguration
    public static class LocalRibbonClientConfiguration {
        @Bean
        public ServerList<Server> ribbonServerList() {
            return new StaticServerList<>(new Server("localhost", wiremock.port()));
        }
    }
}

Ribbon server list need to match the url (host and port) of our WireMock configuration.

Answer 2

Here is an example how to do the wiring of Feign and WireMock with random port (based on Spring-Boot github answer).

@RunWith(SpringRunner.class)
@SpringBootTest(properties = "google.url=http://google.com") // emulate application.properties
@ContextConfiguration(initializers = PortTest.RandomPortInitializer.class)
@EnableFeignClients(clients = PortTest.Google.class)
public class PortTest {

    @ClassRule
    public static WireMockClassRule wireMockRule = new WireMockClassRule(
        wireMockConfig().dynamicPort()
    );

    @FeignClient(name = "google", url = "${google.url}")
    public interface Google {    
        @RequestMapping(method = RequestMethod.GET, value = "/")
        String request();
    }

    @Autowired
    public Google google;

    @Test
    public void testName() throws Exception {
        stubFor(get(urlEqualTo("/"))
                .willReturn(aResponse()
                        .withStatus(HttpStatus.OK.value())
                        .withBody("Hello")));

        assertEquals("Hello", google.request());
    }


    public static class RandomPortInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
        @Override
        public void initialize(ConfigurableApplicationContext applicationContext) {

            // If the next statement is commented out, 
            // Feign will go to google.com instead of localhost
            TestPropertySourceUtils
                .addInlinedPropertiesToEnvironment(applicationContext,
                    "google.url=" + "http://localhost:" + wireMockRule.port()
            );
        }
    }
}

Alternatively you can try playing with System.setProperty() in @BeforeClass method of your test.

Answer 3

There used to be basically two options for doing integration tests for microservices applications:

1. Deployment of services to a test environment and make end-to-end tests
2. Mocking other microservices

First option has the obvious disadvantage of the hassle of deploying all the dependencies (other services, databases, etc) as well. In addition, it is slow and hard to debug.

Second option is faster and has less hassle but it is easy to end up with stubs that behave differently than the reality in time, due to possible code changes. So it is possible to have successful tests but failing app when deployed to prod.

A better solution would be using consumer driven contract verification, so that you will make sure that provider service's API is compliant with the consumer calls. For this purpose, Spring developers can use Spring Cloud Contract. For other environments, there is a framework called PACT. Both can be used with Feign clients as well. Here is an example with PACT.

Answer 4

I personally prefer mockServer to stub any restful API, it is easy to use and is similar to wiremock, but is very powerful compared to the latter.

I have attached the sample code written with groovy/spock for stubbing a GET restful call with mockServer.

First autowire the mockServer instance in test class

@Autowired
private static ClientAndServer mockServer

start the mockServer instance from the setupSpec() method, this method is similar to junit method annotated with @BeforeClass.

def setupSpec() {
     mockServer = ClientAndServer.startClientAndServer(8080)
   }

define the required stub in the corresponding unit test

def "test case"() {
 given:
       new MockServerClient("localhost",8080).when(HttpRequest.request().withMethod("GET").withPath("/test/api").withQueryStringParameters(Parameter.param("param1", "param1_value"), Parameter.param("param2", "param2_value"))).respond(HttpResponse.response().withStatusCode(HttpStatus.OK.value()).withBody("{ message: 'sample response' }"))

 when:
 //your code
 then:
 //your code
}

after the execution of test cases, stop the mock server

def cleanupSpec() {
     mockServer.stop()
} 

Answer 5

I think this is a very interesting yet underrated topic, how to verify your communication channels in a microservice environment. It's literally essential to make sure your channels are working as expected but still, I see tons of projects spending time on testing their Feign clients.

Most of the folks have already answered how to do minimal testing for your Feign clients but let's take it to the next level.

Testing the plain Feign client, the request mapping/response mapping/query mapping/etc is just one tiny part of the picture. In a microservice environment you gotta take care of service resiliency as well, like client-side load balancing, circuit breaking and so on.

Since it's 2021 and Spring Cloud marked Hystrix and Ribbon deprecated, it's time to look at Resilience4J.

I won't put the code here cause it would be probably too much to read but I'll give you some links to one of my GitHub projects.

• Here's a Feign client configuration with Resilience4J for circuit breaking and using time limiters: FeignConfiguration
• Here's a CircuitBreaker test: CircuitBreakerTest
• Here's a TimeLimiter test: TimeLimiterTest
• Here's a client side load balancing test: LoadBalancingTest

Also, this might be a bit much too understand without further explanation yet I can't do it in a single stackoverflow answer, so you can check out a couple of my articles as well as my course on Feign: Mastering microservice communication with Spring Cloud Feign

Answer 6

Probably there is no way to make WireMock comunicate directly with Eureka Server, but you can use other variants to configure test environment that you need.

1. In test environment you can deploy Eureka Service Registry under standalone Jetty servlet container and all the annotations will work like they do in real production environment.
2. If you don't want to use real BarClient endpoint logic, and integration test is only about real http transport layer, then you can use Mockito for BarClient endpoint stub.

I suppose that in order to implement 1 and 2 using Spring-Boot, you will need to make two separate applications for a test environment. One for Eureka Service Registry under Jetty and another for BarClient endpoint stub under Jetty too.

Another solution is to manually configure Jetty and Eureka in test application context. I think that this is a better way but in such case you must to understand what @EnableEurekaServer and @EnableDiscoveryClient annotations do with Spring application context.

Answer 7

Use Spring's RestTemplate instead of feign. RestTemplate is also able to resolve service names via eureka, so you can do something like this:

@Component
public class SomeService {
   @Autowired
   RestTemplate restTemplate;

   public String doSomething() {
     try {
       restTemplate.postForEntity("http://my-service/some/url", 
                                  new BazzleRequest(...), 
                                  Void.class);
       return "so bazzle my eyes dazzle";
     } catch(HttpStatusCodeException e) {
       return "Not bazzle today!";
     }
   }
}

This is way easier testable with Wiremock than feign.