### Question:
MulticastRegistry extends FailbackRegistry { @Override public void unregister(URL url) { super.unregister(url); unregistered(url); } MulticastRegistry(URL url); @Override void doRegister(URL url); @Override void doUnregister(URL url); @Override void doSubscribe(URL url, NotifyListener listener); @Override void doUnsubscribe(URL url, NotifyListener listener); @Override boolean isAvailable(); @Override void destroy(); @Override void register(URL url); @Override void unregister(URL url); @Override void subscribe(URL url, NotifyListener listener); @Override void unsubscribe(URL url, NotifyListener listener); @Override List<URL> lookup(URL url); MulticastSocket getMulticastSocket(); Map<URL, Set<URL>> getReceived();  }### Answer:
@Test public void testUnregister() { Set<URL> registered; registry.register(serviceUrl); registered = registry.getRegistered(); assertTrue(registered.contains(serviceUrl)); registered = registry.getRegistered(); registry.unregister(serviceUrl); assertFalse(registered.contains(serviceUrl)); }