code: @Test public void test_urlHolder_getAdaptiveExtension_UrlNpe() throws Exception {
    Ext2 ext=ExtensionLoader.getExtensionLoader(Ext2.class).getAdaptiveExtension();
    try {
      ext.echo(null,"haha");
      fail();
    }
   catch (  IllegalArgumentException e) {
      assertEquals("org.apache.dubbo.common.extension.ext2.UrlHolder argument == null",e.getMessage());
    }
    try {
      ext.echo(new UrlHolder(),"haha");
      fail();
    }
   catch (  IllegalArgumentException e) {
      assertEquals("org.apache.dubbo.common.extension.ext2.UrlHolder argument getUrl() == null",e.getMessage());
    }
  }
  