The Tor Browser / file revision

 /* Any copyright is dedicated to the Public Domain.

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

 function test() {

   test_tab("about:blank");

   test_tab("about:license");

 }

 function test_tab(url) {

   let originalTab = gBrowser.selectedTab;

   let newTab = gBrowser.addTab(url, {skipAnimation: true});

   is(tabIsActive(newTab), false, "newly added " + url + " tab is not active");

   is(tabIsActive(originalTab), true, "original tab is active initially");

   gBrowser.selectedTab = newTab;

   is(tabIsActive(newTab), true, "newly added " + url + " tab is active after selection");

   is(tabIsActive(originalTab), false, "original tab is not active while unselected");

   gBrowser.selectedTab = originalTab;

   is(tabIsActive(newTab), false, "newly added " + url + " tab is not active after switch back");

   is(tabIsActive(originalTab), true, "original tab is active again after switch back");

   gBrowser.removeTab(newTab);

 }

 function tabIsActive(tab) {

   let browser = tab.linkedBrowser;

   return browser.docShell.isActive;

 }