@Override
    public void subscribe(URL url, NotifyListener listener) {
        if (url == null) {
            throw new IllegalArgumentException("subscribe url == null");
        }
        if (listener == null) {
            throw new IllegalArgumentException("subscribe listener == null");
        }
        if (logger.isInfoEnabled()) {
            logger.info("Subscribe: " + url);
        }
        Set<NotifyListener> listeners = subscribed.computeIfAbsent(url, n -> new ConcurrentHashSet<>());
        listeners.add(listener);
    }
@Test
    void testSubscribeIfListenerNull() {
        Assertions.assertThrows(IllegalArgumentException.class, () -> {
            final AtomicReference<Boolean> notified = new AtomicReference<Boolean>(false);
            NotifyListener listener = urls -> notified.set(Boolean.TRUE);
            URL url = new ServiceConfigURL("dubbo", "192.168.0.1", 2200);
            abstractRegistry.subscribe(url, null);
            Assertions.fail("listener url == null");
        });
    }