anchor.diff:    receive
       {change, Change} ->
         collect_changes(I-1, queue:in(Change, Q))
  -  end.+  end.
  +
  +wait_pids([]) -> ok;
  +wait_pids(Pids) ->
  +  receive
  +    {ok, Pid} -> wait_pids(Pids -- [Pid])
  +  after 5000 -> {error, receive_pids}
  +  end.
  
positive.code:     include_doc,
      collect_changes,
      changes_feed_callback,
      heartbeat_collect_change
    ].
  
  init_per_suite(Config) ->
  
negative.code:   include_doc/1,
    collect_changes/1,
    changes_feed_callback/1,
    heartbeat_collect_change/1,
    multiple_put/1
  ]).
  
  -export([
  