code: @Test(expected=IllegalArgumentException.class) public void testNotifyIfNotifyNull(){
    final AtomicReference<Boolean> notified=new AtomicReference<Boolean>(false);
    NotifyListener listner1=urls -> notified.set(Boolean.TRUE);
    URL url1=new URL("dubbo","192.168.0.1",2200,parametersConsumer);
    abstractRegistry.subscribe(url1,listner1);
    NotifyListener listner2=urls -> notified.set(Boolean.TRUE);
    URL url2=new URL("dubbo","192.168.0.2",2201,parametersConsumer);
    abstractRegistry.subscribe(url2,listner2);
    NotifyListener listner3=urls -> notified.set(Boolean.TRUE);
    URL url3=new URL("dubbo","192.168.0.3",2202,parametersConsumer);
    abstractRegistry.subscribe(url3,listner3);
    List<URL> urls=new ArrayList<>();
    urls.add(url1);
    urls.add(url2);
    urls.add(url3);
    abstractRegistry.notify(url1,null,urls);
    Assert.fail("notify listener == null");
  }
  