Ext2 ext = ExtensionLoader.getExtensionLoader(Ext2.class).getAdaptiveExtension();
Config config = Config.fromKv("protocol", "impl1", "host", "1.2.3.4", "port", "1010", "path", "path1");
String yell = ext.yell(config, "s");
assertEquals("Ext2Impl1-yell", yell);
config = config.addConfig("key1", "impl2");
yell = ext.yell(config, "s");
assertEquals("Ext2Impl2-yell", yell);