nixos: add most basic gnome3 test and take a screenshot

nixos/release-combined.nix

@@ -61,6 +61,7 @@ in rec {
         (all nixos.tests.printing)
         (all nixos.tests.proxy)
         (all nixos.tests.xfce)
+        (all nixos.tests.gnome3)
 
         nixpkgs.tarball
         (all nixpkgs.emacs)

nixos/tests/default.nix

@@ -12,6 +12,7 @@ with import ../lib/testing.nix { inherit system minimal; };
   firewall = makeTest (import ./firewall.nix);
   installer = makeTests (import ./installer.nix);
   efi-installer = makeTests (import ./efi-installer.nix);
+  gnome3 = makeTest (import ./gnome3.nix);
   ipv6 = makeTest (import ./ipv6.nix);
   kde4 = makeTest (import ./kde4.nix);
   #kexec = makeTest (import ./kexec.nix);

nixos/tests/gnome3.nix

@@ -0,0 +1,31 @@
+{ pkgs, ... }:
+
+{
+
+  machine =
+    { config, pkgs, ... }:
+
+    { imports = [ ./common/user-account.nix ];
+
+      services.xserver.enable = true;
+
+      services.xserver.displayManager.auto.enable = true;
+      services.xserver.displayManager.auto.user = "alice";
+      services.xserver.desktopManager.gnome3.enable = true;
+    };
+
+  testScript =
+    ''
+      $machine->waitForX;
+      $machine->sleep(15);
+
+      # Check that logging in has given the user ownership of devices.
+      $machine->succeed("getfacl /dev/snd/timer | grep -q alice");
+
+      $machine->succeed("su - alice -c 'DISPLAY=:0.0 gnome-terminal &'");
+      $machine->waitForWindow(qr/Terminal/);
+      $machine->sleep(10);
+      $machine->screenshot("screen");
+    '';
+
+}