anchor.diff:      lists:map(fun({call, _Mod, Fun, _Args}) -> Fun end, node_commands()).
   
   %% Precondition.
  +node_precondition(_NodeState, {call, ?MODULE, sleep, []}) ->
  +    true;
  +node_precondition(_NodeState, {call, ?MODULE, set_fault, [_Node, _Value]}) ->
  +    true;
   node_precondition(_NodeState, {call, ?MODULE, next_id, [_Node]}) ->
       true;
   node_precondition(_NodeState, _Command) ->
  
positive.code: -define(NAME, fun(Name) -> [{_, NodeName}] = ets:lookup(?ETS, Name), NodeName end).
  
  %% @private
  next_id(Node) ->
      ?PROPERTY_MODULE:command_preamble(Node, [next_id]),
  
      Result = rpc:call(?NAME(Node), paxoid, next_id, [?GROUP], 5000),
  
      ?PROPERTY_MODULE:command_conclusion(Node, [next_id]),
  
      Result.
  
  
negative.code:     % end, Results);
  
      true;
  node_postcondition(_NodeState, {call, ?MODULE, set_fault, [_Node, _Value]}, ok) ->
      true;
  node_postcondition(_NodeState, {call, ?MODULE, sleep, []}, _Result) ->
      true;
  node_postcondition(_NodeState, {call, ?MODULE, next_id, [_Node]}, {badrpc,timeout}) ->
      false;
  node_postcondition(#node_state{counter=Counter}, {call, ?MODULE, next_id, [_Node]}, Value) ->
      node_debug("postcondition received ~p from next_id when value should be: ~p", [Value, Counter + 1]),
  
      case Counter + 1 =:= Value of 
          false ->
              node_debug("********* violation!~n", []),
              ok;
          true ->
              ok
      end,
  
      true;
  node_postcondition(_NodeState, Command, Response) ->
      node_debug("generic postcondition fired (this probably shouldn't be hit) for command: ~p with response: ~p", 
                 [Command, Response]),
  