anchor.diff:          default = {};
         };
   
  -      instances = mkOption {
  +      domains = mkOption {
           default = {};
  -        type = with types; attrsOf (submodule instanceOpts);
  +        type = with types; attrsOf (submodule domainOpts);
         };
   
         extraBuildSteps = mkOption {
  
positive.code:           description = ''
              The main test script. This is run from a separate libvirt machine
              (the test driver machine) that is part of the same network as the
              other libvirt machines (defined by the <code>instances</code>
              option).
            '';
          };
  
negative.code: 
    config = {
  
      libvirt.test.domains.${cfg.test-driver.hostName} = {
        libvirt.domain.name = mkForce "dom-@testid@";
        nixos.modules = cfg.test-driver.extraModules ++ [{
          systemd.services.test-script = {
  