anchor.diff:        $machine->mustSucceed("echo hello");
         $machine->shutdown;
       '';
  +
   }
  
positive.code:           "mount LABEL=nixos /mnt",
        );
  
        $machine->shutdown;
  
        # Now see if we can boot the installation.
  
negative.code:       $machine->waitForJob("tty1");
        $machine->waitForJob("rogue");
        $machine->waitForJob("nixos-manual");
  
        # Test nix-env.
        $machine->mustSucceed("source /etc/profile");
        $machine->mustFail("hello");
        $machine->mustSucceed("nix-env -i hello");
        $machine->mustSucceed("hello") =~ /Hello, world/
            or die "bad `hello' output";
  
        # Partition the disk.
        $machine->mustSucceed(
  