anchor.diff:      lists:sort(orddict:to_list(S#qcst.d)) =:= lists:sort(R);
   postcondition(_From,_To,S,_C={call,_M,is_empty,[_BeState]},R) ->
       R =:= (orddict:size(S#qcst.d) =:= 0);
  +postcondition(_From,_To,S,_C={call,_M,list_bucket,[_BeState,Bucket]},R) ->
  +    AllKeys = orddict:fetch_keys(S#qcst.d),
  +    R =:= lists:sort([K || {B,K} <- AllKeys, B =:= Bucket]);
   postcondition(_From,_To,_S,_C,_R) ->
       true.
  -
   
   
   init_backend(Backend, Config) ->
  
positive.code:                       begin
                            {H,{_F,S},Res} = run_commands(?MODULE, Cmds),
                            Cleanup(S#qcst.s, sets:to_list(S#qcst.olds)),
                            ?WHENFAIL(io:format("History\n~p\nState\n~p\nResult: ~p\n", [H,S,Res]),
                                      Res == ok)
                        end)).
  
  
  
negative.code:      {history, {call,Backend,list,[S#qcst.s]}},
       {history, {call,?MODULE,fold,[Backend,S#qcst.s]}},
       {history, {call,Backend,is_empty,[S#qcst.s]}},
       {history, {call,Backend,list_bucket,[S#qcst.s,bucket()]}},
       {{stopped, Backend, Volatile}, {call,Backend,drop,[S#qcst.s]}},
       {{stopped, Backend, Volatile}, {call,Backend,stop,[S#qcst.s]}}
      ].
  