code: @Test public void testListener() throws Exception {
    ReferenceConfig referenceConfig=new ReferenceConfig();
    referenceConfig.setListener("mockinvokerlistener");
    assertThat(referenceConfig.getListener(),equalTo("mockinvokerlistener"));
    Map<String,String> parameters=new HashMap<String,String>();
    parameters.put(Constants.INVOKER_LISTENER_KEY,"prelistener");
    AbstractInterfaceConfig.appendParameters(parameters,referenceConfig);
    assertThat(parameters,hasValue("prelistener,mockinvokerlistener"));
  }
  