code: @Test public void assertAddConnectionStateListener(){
    CuratorFramework client=mock(CuratorFramework.class);
    @SuppressWarnings("unchecked") Listenable<ConnectionStateListener> listeners=mock(Listenable.class);
    ConnectionStateListener listener=mock(ConnectionStateListener.class);
    when(client.getConnectionStateListenable()).thenReturn(listeners);
    when(regCenter.getRawClient()).thenReturn(client);
    jobNodeStorage.addConnectionStateListener(listener);
    verify(listeners).addListener(listener);
  }
  