anchor.diff:          {error, Reason, Req2} ->
               Reply = jsx:encode([{error, Reason}]),
               Req3 = cowboy_req:set_resp_body(Reply, Req2),
  -            {false, Req3, #state{}}
  +            {false, Req3, State}
       end.
   
   %% internal function
   -spec get_vars_from_body(cowboy_req:req()) ->
  -    {ok | error, state() | wrong_json, cowboy_req:req()}.
  +    {ok, {binary(), binary()}, cowboy_req:req()} | 
  +    {error, wrong_json, cowboy_req:req()}.
   get_vars_from_body(Req) ->
       {ok, Body, Req2} = cowboy_req:body(Req),
       try
  
positive.code: 
  -spec to_json(cowboy_req:req(), state()) -> 
      {jsx:json_text(), cowboy_req:req(), state()}.
  to_json(Req0, State = #state{}) ->
      {ok, Filenames} = file:list_dir("scenarios"),
      Filenames2 =
          lists:filter(
  
negative.code: 
  -spec rest_init(cowboy_req:req(), [atom()]) -> {ok, cowboy_req:req(), state()}.
  rest_init(Req, _Opts) ->
      {ok, Req, []}.
  
  -spec allowed_methods(cowboy_req:req(), state()) -> 
      {[binary()], cowboy_req:req(), state()}.
  