anchor.diff:    # The test script boots the CD, installs NixOS on an empty hard
     # disk, and then reboot from the hard disk.  It's parameterized with
     # a test script fragment `createPartitions', which must create
  -  # partitions and filesystems, and a configuration.nix fragment
  -  # `fileSystems'.
  -  testScriptFun = { createPartitions, fileSystems, testChannel, grubVersion, grubDevice }:
  +  # partitions and filesystems.
  +  testScriptFun = { createPartitions, testChannel, grubVersion, grubDevice }:
       let iface = if grubVersion == 1 then "scsi" else "virtio"; in
       ''
         createDisk("harddisk", 4 * 1024);
  
positive.code:       }
      '';
  
    rootFS =
      ''
        fileSystems."/".device = "/dev/disk/by-label/nixos";
      '';
  
    bootFS =
      ''
        fileSystems."/boot".device = "/dev/disk/by-label/boot";
      '';
  
  
    # Configuration of a web server that simulates the Nixpkgs channel
    # distribution server.
  
negative.code: 
  
    makeInstallerTest =
      { createPartitions, testChannel ? false, grubVersion ? 2, grubDevice ? "/dev/vda" }:
      makeTest {
        inherit iso;
        nodes = if testChannel then { inherit webserver; } else { };
        testScript = testScriptFun {
          inherit createPartitions testChannel grubVersion grubDevice;
        };
      };
  
  