anchor.diff:    config = {
   
       libvirt.test.instances.test-driver = {
  -      libvirt.name = mkForce "@uuid@";
  -      libvirt.fileShares.out = {
  -        guestPath = "/out";
  -        hostPath = "out";
  -        readOnly = false;
  -      };
  +      libvirt.name = mkForce "@testid@";
         nixos.modules = cfg.test-driver.extraModules ++ [{
  -        systemd.services.test-driver = {
  +        systemd.services.test-script = {
             wantedBy = [ "multi-user.target" ];
             wants = [ "network.target" ];
             after = [ "network.target" ];
  
positive.code:           mappedGid = "@gid@";
            rootPath = "root-${name}";
          };
          name = "${name}-@uuid@";
          netdevs.eth0 = {
            mac = null;
            network = "net-@uuid@";
          };
          consoleFile = "@pwd@/out/logs/${name}.console";
          extraDevices = ''
            <serial type='file'>
              <source path='@pwd@/out/logs/${name}.journal'/>
              <target port='1'/>
            </serial>
          '';
        };
  
        nixos.modules = singleton {
  
negative.code:       instances = mkOption {
          default = {};
          type = with types; attrsOf (submodule instanceOpts);
        };
  
        verification-script = mkOption {
          type = types.lines;
          description = ''
            A script that will be inlined in the build phase of the
            result builder. The environment variable <code>output</output>
            will point to the directory containing the build output.
            By default, the output is checked for the existence of a
            successful exit code file from the test script.
            You can also use this script to do post-processing of the
            test output, by writing to the <code>out</code> path like
            any Nix build.
          '';
          default = ''
            test -a hosts/test-driver/script.exit && \
            test "$(cat hosts/test-driver/script.exit)" = "0" || \
            exit 1
          '';
        };
  
        test-driver = {
  