anchor.diff: -{ system ? builtins.currentSystem, debug ? false }:
  +{ system ? builtins.currentSystem, debug ? false, enableUnfree ? false }:
   
   with import ../lib/testing.nix { inherit system; };
   with pkgs.lib;
  
positive.code:     destroyVM_test1;
      destroyVM_test2;
    '';
  } // mapAttrs (mkVBoxTest true vboxVMsWithExtpack) {
    enable-extension-pack = ''
      createVM_testExtensionPack;
      vbm("startvm testExtensionPack");
      waitForStartup_testExtensionPack;
      $machine->screenshot("cli_started");
      waitForVMBoot_testExtensionPack;
      $machine->screenshot("cli_booted");
  
      $machine->nest("Checking for privilege escalation", sub {
        $machine->fail("test -e '/root/VirtualBox VMs'");
        $machine->fail("test -e '/root/.config/VirtualBox'");
        $machine->succeed("test -e '/home/alice/VirtualBox VMs'");
      });
  
      shutdownVM_testExtensionPack;
      destroyVM_testExtensionPack;
    '';
  }
  
negative.code:     meta = with pkgs.stdenv.lib.maintainers; {
        maintainers = [ aszlig wkennington cdepillabout ];
      };
    };
  
    unfreeTests = mapAttrs (mkVBoxTest true vboxVMsWithExtpack) {
      enable-extension-pack = ''
        createVM_testExtensionPack;
        vbm("startvm testExtensionPack");
        waitForStartup_testExtensionPack;
        $machine->screenshot("cli_started");
        waitForVMBoot_testExtensionPack;
        $machine->screenshot("cli_booted");
  
        $machine->nest("Checking for privilege escalation", sub {
          $machine->fail("test -e '/root/VirtualBox VMs'");
          $machine->fail("test -e '/root/.config/VirtualBox'");
          $machine->succeed("test -e '/home/alice/VirtualBox VMs'");
        });
  
        shutdownVM_testExtensionPack;
        destroyVM_testExtensionPack;
      '';
    };
  
  in mapAttrs (mkVBoxTest false vboxVMs) {
  