protected Collection<ItemHolder> items()
    {
        return new HashSet<>(items.values());
    }
@Test(timeout = 5000)
    public void testItems()
    {
        ZContext ctx = new ZContext();
        ZPoller poller = new ZPoller(ctx);
        try {
            Socket socket = ctx.createSocket(SocketType.XPUB);
            Iterable<ItemHolder> items = poller.items(null);
            assertThat(items, notNullValue());

            ItemHolder holder = poller.create(socket, null, 0);
            poller.register(holder);
            items = poller.items(socket);
            assertThat(items, hasItem(holder));
        }
        finally {
            poller.close();
            ctx.close();
        }
    }