@Test
  public void useServiceWithoutStartTest() throws Exception {
    frontendRestRequestService = getFrontendRestRequestService();
    frontendRestRequestService.setupResponseHandler(responseHandler);
    // not fine to use without start.
    for (RestMethod method : RestMethod.values()) {
      if (method.equals(RestMethod.UNKNOWN)) {
        continue;
      }
      verifyOperationFailure(createRestRequest(method, "/", null, null), RestServiceErrorCode.ServiceUnavailable);
    }
  }
This tests for exceptions thrown when an {@link FrontendRestRequestService} instance is used without calling
{@link FrontendRestRequestService#start()} first.
@throws Exception
ambry-frontend/src/test/java/com/github/ambry/frontend/FrontendRestRequestServiceTest.java