### Question:
NatService { public boolean isNatEnvironment() { return currentNatMethod != NatMethod.NONE; } NatService(final Optional<NatManager> natManager, final boolean fallbackEnabled);  NatService(final Optional<NatManager> natManager); boolean isNatEnvironment(); void ifNatEnvironment(
      final NatMethod natMethod, final Consumer<? super NatManager> action); NatMethod getNatMethod(); Optional<NatManager> getNatManager(); void start(); void stop(); String queryExternalIPAddress(final String fallbackValue); String queryLocalIPAddress(final String fallbackValue); Optional<NatPortMapping> getPortMapping(
      final NatServiceType serviceType, final NetworkProtocol networkProtocol); static NatMethod autoDetectNatMethod(final NatMethodDetector... natMethodDetectors);  }### Answer:
@Test public void assertThatIsNatEnvironmentReturnCorrectStatus() { final NatService nonNatService = new NatService(Optional.empty(), true); assertThat(nonNatService.isNatEnvironment()).isFalse(); final NatService upnpNatService = new NatService(Optional.of(new UpnpNatManager()), true); assertThat(upnpNatService.isNatEnvironment()).isTrue(); }