@BeforeClass
  public static void startRequestResponseHandler() throws InstantiationException, IOException {
    verifiableProperties = new VerifiableProperties(new Properties());
    router = new InMemoryRouter(verifiableProperties, new MockClusterMap(), null);
    restRequestService = new MockRestRequestService(verifiableProperties, router);
    asyncRequestResponseHandler =
        new AsyncRequestResponseHandler(new RequestResponseHandlerMetrics(new MetricRegistry()), 5, restRequestService);
    restRequestService.setupResponseHandler(asyncRequestResponseHandler);
    restRequestService.start();
    asyncRequestResponseHandler.start();
  }
Sets up all the tests by providing a started {@link AsyncRequestResponseHandler} for their use.
@throws InstantiationException
@throws IOException
ambry-rest/src/test/java/com/github/ambry/rest/AsyncRequestResponseHandlerTest.java