anchor.diff:      Ops = [],
       {ok, PNCounter2, ignore} = materialize(crdt_pncounter, PNCounter, ignore,
                                   vectorclock:from_list([{1,1}]),
  -                                Ops, ignore, ignore),
  +                                Ops, ignore),
       ?assertEqual(0,crdt_pncounter:value(PNCounter2)).
   
   materializer_eager_clocksi_test()->
  
positive.code:     {ok, PNCounter2, CommitTime2} = materialize(crdt_pncounter,
                                        PNCounter, ignore,
                                        vectorclock:from_list([{2,2},{1,2}]),
                                        Ops, ignore, ignore),
      ?assertEqual({4, {2,1}}, {crdt_pncounter:value(PNCounter2), CommitTime2}),
      
      
  
negative.code:   InSnapshot = OpCommitTime =< Ts,
    case SnapshotCommitTime of
      ignore -> 
      	  InSnapshot;
      {_SnapshotDc, _SnapshotCT} ->
  		    InSnapshot andalso is_smaller(SnapshotCommitTime, OperationCommitTime)
  	end.
  
  %% @doc Checks whether a commit time is smaller than another one.
  