### Question:
ConfigObserver { public ConfigObserver onInetSocketAddress(String key, int defaultPort, ConfigValueListener<InetSocketAddress> listener) { return onInetSocketAddress(key, new InetSocketAddress(defaultPort), listener); } ConfigObserver(String applicationName);  ConfigObserver(File configDirectory, String applicationName);  ConfigObserver(File configDirectory, String applicationName, List<String> profiles);  ConfigObserver(ConfigLoader configLoader); ConfigObserver onConfigChange(ConfigListener listener); ConfigObserver onSingleConfigValue(String key, Function<String, T> transformer, T defaultValue, ConfigValueListener<T> listener); ConfigObserver onStringValue(String key, String defaultValue, ConfigValueListener<String> listener); ConfigObserver onIntValue(String key, int defaultValue, ConfigValueListener<Integer> listener); ConfigObserver onLongValue(String key, long defaultValue, ConfigValueListener<Long> listener); ConfigObserver onInetSocketAddress(String key, int defaultPort, ConfigValueListener<InetSocketAddress> listener); ConfigObserver onInetSocketAddress(String key, InetSocketAddress defaultAddress, ConfigValueListener<InetSocketAddress> listener); ConfigObserver onDurationValue(String key, Duration defaultValue, ConfigValueListener<Duration> listener); ConfigObserver onStringListValue(String key, String defaultValue, ConfigValueListener<List<String>> listener); ConfigObserver onPrefixedValue(String prefix, ConfigValueListener<Map<String, String>> listener); ConfigObserver onPrefixedValue(String prefix, ConfigListener.Transformer<T> transformer, ConfigValueListener<T> listener); ConfigObserver onPrefixedOptionalValue(String prefix, ConfigListener.Transformer<T> transformer, ConfigValueListener<Optional<T>> listener); ConfigObserver onPrefixedOptionalValue(String prefix, ConfigValueListener<Optional<Map<String, String>>> listener); void updateConfiguration(Map<String, String> newConfiguration);  }### Answer:
@Test public void shouldListenToInetAddresses() { observer.onInetSocketAddress("httpListenAddress", 10080, address -> this.httpListenAddress = address ); assertThat(httpListenAddress).isEqualTo(new InetSocketAddress(10080)); writeConfigLine("httpListenAddress=127.0.0.1:11080"); assertThat(httpListenAddress).isEqualTo(new InetSocketAddress("127.0.0.1", 11080)); writeConfigLine("httpListenAddress=12080"); assertThat(httpListenAddress).isEqualTo(new InetSocketAddress("0.0.0.0", 12080)); writeConfigLine("httpListenAddress=:13080"); assertThat(httpListenAddress).isEqualTo(new InetSocketAddress("0.0.0.0", 13080)); }