gecko-dev/netwerk/test/unit/test_bug935499.js

"use strict";

function run_test() {
  var idnService = Cc["@mozilla.org/network/idn-service;1"].getService(
    Ci.nsIIDNService
  );

  var isASCII = {};
  Assert.equal(idnService.convertToDisplayIDN("xn--", isASCII), "xn--");
}