anchor.diff:  -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
            terminate/2, code_change/3]).
   
  --record(state, {nodes}).
  +-record(state, {nodes, timer}).
   
   -include_lib("eunit/include/eunit.hrl").
   
  
positive.code:     do_nodes_wanted_updated(do_nodes_wanted()),
      % Register for nodeup/down messages as handle_info callbacks.
      ok = net_kernel:monitor_nodes(true),
      % Track the last list of actual ndoes.
      {ok, #state{nodes = false}}.
  
  terminate(_Reason, _State)     -> ok.
  code_change(_OldVsn, State, _) -> {ok, State}.
  handle_cast(_Msg, State)       -> {noreply, State}.
  
  
negative.code: -module(ns_node_disco).
  
  -behaviour(gen_server).
  
  -define(PING_FREQ, 60000).
  
  %% API
  -export([start_link/0,
  