gecko-dev/chrome/test/unit/head_crtestutils.js

const XULAPPINFO_CONTRACTID = "@mozilla.org/xre/app-info;1";
const XULAPPINFO_CID = Components.ID("{4ba645d3-be6f-40d6-a42a-01b2f40091b8}");

function registerManifests(manifests) {
  var reg = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
  for (var manifest of manifests) {
    reg.autoRegister(manifest);
  }
}