anchor.diff:      Op4 = #clocksi_payload{key = abc, type = crdt_pncounter,
                              op_param = {update,{{increment,2},1}},
                              commit_time = {1, 4}, txid = 4},
  -
  -    Ops = [Op1,Op2,Op3,Op4],
  +    Ops = [Op1, Op2, Op3, Op4],
  +
       {ok, PNCounter2, CommitTime2} = materialize(crdt_pncounter,
                                         PNCounter, ignore, vectorclock:from_list([{1,3}]),
                                         Ops, ignore),
  
positive.code: materializer_clocksi_test()->
      PNCounter = new(crdt_pncounter),
      ?assertEqual(0,crdt_pncounter:value(PNCounter)),
      Op1 = #clocksi_payload{key = abc, type = crdt_pncounter,
                             op_param = {update,{{increment,2},1}},
                             commit_time = {1, 1}, txid = 1},
  
negative.code:             materialize(Type, Snapshot, SnapshotCommitTime, SnapshotTime, Rest, TxId, LastOpCommitTime)
      end.
  
  %% @doc Checks whether a commit time is included in a snapshot time and, if not ignored,
  %%		whether the commit time is more recent than some commit time.
  -spec is_op_in_snapshot(commit_time(), snapshot_time(), commit_time() | ignore) -> boolean().
  is_op_in_snapshot(OperationCommitTime, SnapshotTime, SnapshotCommitTime) ->
  	{OpDc, OpCommitTime} = OperationCommitTime,
      {ok, Ts} = vectorclock:get_clock_of_dc(OpDc, SnapshotTime),
      case SnapshotCommitTime of
      ignore -> 
  