anchor.diff:        {config, pkgs, ...}:
         {
           fileSystems = pkgs.lib.mkOverride 50 {} 
  -        [ 
  -          { mountPoint = "/repos";
  -            device = "storage:/repos"; } 
  -        ];
  +          [ { mountPoint = "/repos";
  +              device = "storage:/repos"; } 
  +          ];
         
           services.portmap.enable = true;
           services.httpd.enable = true;
  
positive.code:       $webserver->mustSucceed("PYTHONPATH=${pkgs.pythonPackages.psycopg2}/lib/python2.5/site-packages trac-admin /var/trac/projects/test initenv Test postgres://root\@postgresql/trac svn /repos/trac");
        
        $client->waitForFile("/tmp/.X11-unix/X0");
        sleep 60;
        
        $client->execute("su - alice -c 'DISPLAY=:0.0 konqueror http://webserver/projects/test &'");
        sleep 120;
        
        $client->screenshot("screen");
      '';
  
negative.code:     client = 
        {config, pkgs, ...}:
        {
          require = [ ./common/x11.nix ];
          services.xserver.desktopManager.kde4.enable = true;
        };
    };
      
  