The Tor Browser / file revision

 /* Any copyright is dedicated to the Public Domain.

    http://creativecommons.org/publicdomain/zero/1.0/ */

 function test() {

   waitForExplicitFinish();

   newWindowWithTabView(function (win) {

     registerCleanupFunction(function () win.close());

     let cw = win.TabView.getContentWindow();

     let groupItems = cw.GroupItems.groupItems;

     let groupItem = groupItems[0];

     is(groupItems.length, 1, "There is one group item on startup");

     whenTabViewIsHidden(function () {

       is(groupItems.length, 1, "There is still one group item");

       isnot(groupItem.id, groupItems[0].id, 

             "The initial group item is not the same as the final group item");

       is(win.gBrowser.tabs.length, 1, "There is only one tab");

       finish();

     }, win);

     hideGroupItem(groupItem, function () {

       // create a new tab

       EventUtils.synthesizeKey("t", { accelKey: true }, cw);

     });

   });

 }