anchor.diff:  
   %% API
   -export([start_link/0,
  +         stop/0,
            reset/0,
            filter/2,
            collect/0, collect/1, collect/2,
  -         results/0]).
  +         results/0,
  +         stop_collect/0]).
   -export([test_all_events/1]).
   
   -export([all_events/1]).
  +-export([trigger_sentinel/0]).
   
   %% gen_server callbacks
   -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
  
positive.code: -record(state, {trace=[],
                  filters=[],
                  mfs=[],
                  stop_tref}).
  
  %%===================================================================
  %% API
  
negative.code: 
  start_link() ->
      gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
  
  stop() ->
      gen_server:call(?SERVER, stop).
  
  reset() ->
      gen_server:call(?SERVER, reset).
  