### Question:
UpnpNatManager extends AbstractNatManager { @VisibleForTesting synchronized CompletableFuture<RemoteService> getWANIPConnectionService() { checkState(isStarted(), "Cannot call getWANIPConnectionService() when in stopped state"); return getService(SERVICE_TYPE_WAN_IP_CONNECTION); } UpnpNatManager();   UpnpNatManager(final UpnpService service); @Override synchronized void doStart(); @Override synchronized void doStop(); @Override CompletableFuture<String> retrieveExternalIPAddress(); @Override CompletableFuture<List<NatPortMapping>> getPortMappings(); void requestPortForward(
      final int port, final NetworkProtocol protocol, final NatServiceType serviceType);  }### Answer:
@Test public void registryListenerShouldDetectService() throws Exception { upnpManager.start(); ArgumentCaptor<RegistryListener> captor = ArgumentCaptor.forClass(RegistryListener.class); verify(mockedRegistry).addListener(captor.capture()); RegistryListener listener = captor.getValue(); assertThat(listener).isNotNull(); RemoteService wanIpConnectionService = new RemoteService( new UDAServiceType("WANIPConnection"), new UDAServiceId("WANIPConnectionService"), URI.create("/x_wanipconnection.xml"), URI.create("/control?WANIPConnection"), URI.create("/event?WANIPConnection"), null, null); RemoteDevice device = new RemoteDevice( new RemoteDeviceIdentity( UDN.valueOf(UpnpNatManager.SERVICE_TYPE_WAN_IP_CONNECTION), 3600, new URL("http: null, InetAddress.getByName("127.63.31.15")), new UDADeviceType("WANConnectionDevice"), new DeviceDetails("WAN Connection Device"), wanIpConnectionService); listener.remoteDeviceAdded(mockedRegistry, device); assertThat(upnpManager.getWANIPConnectionService().join()).isEqualTo(wanIpConnectionService); }