anchor.diff:  	Json3 = purge_undef(Json2),
   	ibrowse:send_req(?zone_url, [owner_cookie(), ?accepts, ?contenttype], put, jsx:to_json(Json3)).
   
  +create_aura(Aura, Name, Next, Who, State) ->
  +	#state{auras = Auras} = State,
  +	NextZoneId = get_next(Next, Auras),
  +	Json = [{<<"next_zone_id">>, NextZoneId} | Aura],
  +	Json2 = [{<<"name">>, Name} | proplists:delete(<<"name">>, Json)],
  +	Json3 = purge_undef(Json2),
  +	Cookie = cookie(Who),
  +	ibrowse:send_req(?aura_url, [Cookie, ?accepts, ?contenttype], put, jsx:to_json(Json3)).
  +
   delete_zone(Nth, State) ->
   	#state{zones = Zones} = State,
   	Zone = lists:nth(Nth, Zones),
  
positive.code: postcondition(State, {call, _, create_zone, [Put, Name, Next, _]}, {ok, "201", _, Body}) ->
  	#state{zones = Zones} = State,
  	NextZoneId = get_next(Next, Zones),
  	Json = [{<<"next_zone_id">>, NextZoneId} | Put],
  	Json2 = [{<<"name">>, Name} | proplists:delete(<<"name">>, Json)],
  	Json3 = purge_undef(Json2),
  
negative.code: 
  precondition(S, {call, _, create_zone, _}) ->
  	true;
  precondition(S, {call, _, create_aura, _}) ->
  	true;
  precondition(S, {call, _, delete_zone, [_, #state{zones = Z}]}) when length(Z) >= 1 ->
  	true;
  precondition(_,_) ->
  