add_task(async function test() { window.open("about:blank", "", "width=100,height=100,noopener"); let win = Services.wm.getMostRecentWindow("navigator:browser"); Services.prefs.setBoolPref("browser.tabs.closeWindowWithLastTab", false); win.gBrowser.removeCurrentTab(); ok(win.closed, "popup is closed"); // clean up if (!win.closed) { win.close(); } Services.prefs.clearUserPref("browser.tabs.closeWindowWithLastTab"); });