anchor.diff:      %% unexpected
       {next_state, passive, S}.
   
  +passive({enqueue, Msg}, From, S = #state{}) ->
  +    gen_fsm:reply(From, ok),
  +    {next_state, passive, insert(Msg, S)}.
  +
   %% @private
   notify(active, S = #state{size=0}) ->
       {next_state, active, S};
  
positive.code: %% @doc Enqueues a message.
  -spec enqueue(pid(), term()) -> ok.
  enqueue(Queue, Msg) ->
      gen_fsm:send_event(Queue, {enqueue, Msg}).
  
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  %%% gen_fsm Function Definitions %%%
  
negative.code:          active/1, notify/1, enqueue/2]).
  -export([init/1,
           active/2, passive/2, notify/2,
           active/3, passive/3, notify/3,
           handle_event/3, handle_sync_event/4, handle_info/3,
           terminate/3, code_change/4]).
  
  