The Tor Browser / file revision

 /* Any copyright is dedicated to the Public Domain.

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

 function test() {

   waitForExplicitFinish();

   newWindowWithTabView(onTabViewShown);

 }

 function onTabViewShown(win) {

   let contentWindow = win.TabView.getContentWindow();

   let finishTest = function () {

     hideTabView(function () {

       win.close();

       finish();

     }, win);

   }

   // do not let the group arrange itself

   contentWindow.GroupItems.pauseArrange();

   // let's create a groupItem small enough to get stacked

   let groupItem = new contentWindow.GroupItem([], {

     immediately: true,

     bounds: {left: 20, top: 20, width: 100, height: 100}

   });

   contentWindow.UI.setActive(groupItem);

   // we need seven tabs at least to reproduce this

   for (var i=0; i<7; i++)

     win.gBrowser.loadOneTab('about:blank', {inBackground: true});

   // finally let group arrange

   contentWindow.GroupItems.resumeArrange();

   let tabItem6 = groupItem.getChildren()[5];

   let tabItem7 = groupItem.getChildren()[6];  

   ok(!tabItem6.getHidden(), 'the 6th child must not be hidden');

   ok(tabItem7.getHidden(), 'the 7th child must be hidden');

   finishTest();

 }