在单元测试用例 Spring 引导期间模拟 API 调用

Question

I have two microservices Microservice A ( context path - /abc ) and microservice B (context path - /def )

Example URLs: test.domain.com/abc/endpoint1,test.domain.com/def/endpoint2

In one of the apis of Microservice A ( test.domain.com/abc/endpoint1) internally its making call to Microservice B (/def/endpoint2) -> the prefix for this internal call is generated as follows (Extract the domain from the request and then append /def/endpoint2 to make a rest call the total url will become as (test.domain.com/def/endpoint2)

Problem: When we are writting unit test cases starting controller level we are using TestRestTemplate For this testing we need to use http://localhost: portnumber /abc/endpoint1 to test..

Now the url of the def service also will be derived as http://localhost: portnumber /def/endpoint2 How to mock this response ( Note: We cannot use mock server on same port, we will get port binding exception). Is there any workaround for the same?

Is there any way to have gateway kind of setup while using TestRestTemplate to route http://localhost:portnumber/def/* calls to get response from mockserver and http://localhost:portnumber/abc/* to make the actual API Service under test?

Answer 1

You could use a ClientHttpRequestInterceptor for this and manipulate the actual URI to call if it matches the path of your second microservice.

This might be a naive protoypish implementation :

public class UrlRewriter implements ClientHttpRequestInterceptor {
  @Override
  public ClientHttpResponse intercept(HttpRequest httpRequest, byte[] bytes, ClientHttpRequestExecution clientHttpRequestExecution) throws IOException {
    try {
      if (httpRequest.getURI().toString().contains("/def/abc")) {
        HttpRequest modifiedRequest = new MockClientHttpRequest(HttpMethod.GET, new URI("http://localhost:8888/def/abc"));
        return clientHttpRequestExecution.execute(modifiedRequest, bytes);
      } else {
        return clientHttpRequestExecution.execute(httpRequest, bytes);
      }

    } catch (URISyntaxException e) {
      e.printStackTrace();
      return null;
    }
  }
}

And then you can provide a custom bean of type RestTemplateBuilder for your test that is picked up by the TestRestTemplate :

@SpringBootTest(webEnvironment = RANDOM_PORT)
public class TestOne {


  @TestConfiguration
  static class TestConfig {

    @Bean
    public RestTemplateBuilder restTemplateBuilder() {
      return new RestTemplateBuilder().interceptors(new UrlRewriter());
    }

  }

  @Autowired
  private TestRestTemplate testRestTemplate;

  @Test
  public void test() {
    assertNotNull(testRestTemplate);

    testRestTemplate.getForObject("/abc/endpoint1", String.class);
  }
}