Cross Platform GUI Automation tool Linux version is LDTP, Windows version is Cobra and Mac version is PyATOM.
Linux GUI testing is known to work on GNOME / KDE (QT >= 4.8) / Java Swing / LibreOffice / Mozilla application on all major Linux distribution
Windows GUI testing is known to work on application written in .NET / C++ / Java / QT on Windows XP SP3 / Vista SP2 / Windows 7 / Windows 8 development version
Mac GUI testing is known to work on OS X Snow Leopard/Lion/Mountain Lion. Where ever ATOMac runs, LDTP should work on it
The GNU/Linux Desktop (GUI Application) Testing Project (GNU LDTP) aimed at producing high quality test automation framework and cutting-edge tools that can be used to test and improve the GNU/Linux or Solaris desktops. It uses the Accessibility libraries to discover through the application’s user interface.