### Question:
ConfigObserver { public ConfigObserver onStringListValue(String key, String defaultValue, ConfigValueListener<List<String>> listener) { return onSingleConfigValue(key, ConfigObserver::parseStringList, defaultValue != null ? parseStringList(defaultValue) : null, 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 shouldReadStringList() { List<String> list = new ArrayList<>(); observer.onStringListValue("prop", "foo,bar", l -> { list.clear(); list.addAll(l); }); assertThat(list).containsExactly("foo", "bar"); writeConfigLine("prop=a, b ,c"); assertThat(list).containsExactly("a", "b", "c"); }