gecko-dev/xpcom/tests/xptinfo/xptunit/test_jar_xptloading.js

function run_test()
{
  const xptiITestInterface_IID = "{13c9fc33-40e6-44dc-81e2-21e0dd41f232}";

  var id = Components.interfaces.xptiITestInterface;
  do_check_true(id != undefined, "xptiITestInterface not registered");

  var id2 = Components.interfacesByID[xptiITestInterface_IID];
  do_check_true(id.toString() == id2, "xptiITestInterface info doesn't match");
}