ConfigFactory { public static String clearProperty(String key) { return INSTANCE.clearProperty(key); } private  ConfigFactory(); static Factory newInstance(); static T create(Class<? extends T> clazz, Map<?, ?>... imports); static String setProperty(String key, String value); static Properties getProperties(); static void setProperties(Properties properties); static String getProperty(String key); static String clearProperty(String key); static void registerLoader(Loader loader); static void setTypeConverter(Class<?> type, Class<? extends Converter<?>> converter); static void removeTypeConverter(Class<?> type);  }
@Test(expected = IllegalArgumentException.class) public void testClearPropertyNullKey() { ConfigFactory.clearProperty(null); }
@Test(expected = IllegalArgumentException.class) public void testClearPropertyEmptyKey() { ConfigFactory.clearProperty(""); }