anchor.diff:  		{call, ?MODULE, update_bad_user, [rpgb_prop:g_name(), g_next(S), g_url(), g_existant(S)]},
   		{call, ?MODULE, update_blank_name, [g_next(S), g_url(), g_existant(S)]},
   		{call, ?MODULE, update, [oneof([undefined, rpgb_prop:g_name()]), g_next(S), g_existant(S), g_url()]},
  -		{call, ?MODULE, update_bad_reorder, [choose(90000, 100000), g_existant(S)]},
  +		{call, ?MODULE, update_bad_reorder, [choose(90000, 100000), g_existant(S), g_url()]},
   		{call, ?MODULE, delete_bad_user, [g_url(), g_existant(S)]},
   		{call, ?MODULE, delete_last_layer, [g_url(), g_existant(S)]},
   		{call, ?MODULE, delete, [g_url(), g_existant(S)]}
  
positive.code: %% =======================================================
  
  create_bad_user(Name, Next, UrlType) ->
  	false.
  
  create_blank_name(Next, UrlType) ->
  	false.
  
  create_name_conflict(Next, Existant, UrlType) ->
  	false.
  
  create_missing_map_id(Name, Next) ->
  	false.
  
  create_bad_map_id(Name, Next, MapId, UrlType) ->
  	false.
  
  create(Name, Next, UrlType) ->
  	false.
  
  get_layers() ->
  	false.
  
  get_a_layer(UrlType, Layer) ->
  	false.
  
  update_bad_user(Name, Next, UrlType, Layer) ->
  	false.
  
  update_blank_name(Next, UrlType, Layer) ->
  	false.
  
  update(Name, Next, Layer, UrlType) ->
  	false.
  
  update_bad_reorder(BadNext, Layer) ->
  	false.
  
  delete_bad_user(UrlType, Layer) ->
  	false.
  
  delete_last_layer(UrlType, Layer) ->
  	false.
  
  delete(UrlType, Layer) ->
  	false.
  
  %% =======================================================
  %% postcondition
  
negative.code: -define(map_url(LayerId), ?map_url ++ "/" ++ integer_to_list(LayerId)).
  -define(layer_url, "http://localhost:9097/layer").
  -define(layer_url(LayerId), ?layer_url ++ "/" ++ integer_to_list(LayerId)).
  -define(mapid, 9000).
  -define(cookie, begin
  	{_Head, Cookie} = cowboy_cookies:cookie(<<"rpgbsid">>, <<"sessionid">>),
  	{"Cookie", binary_to_list(Cookie)}
  