anchor.diff:      _ = unittest_helper:end_per_suite(Config),
       ok.
   
  +-define(EPSILON, 0.1).
  +
   -spec prop_add_keys(BaseKey::?RT:key(), Size::1..50, Values::[?RT:key(),...]) -> true.
   prop_add_keys(BaseKey, Size, Values0) ->
       H = histogram_rt:create(Size, BaseKey),
  
positive.code:     H2 = histogram_rt:add(Key1, H),
      H3 = histogram_rt:add(Key2, H2),
      %% check results
      case nodelist:succ_ord_id(Key1, Key2, BaseKey) of
          true -> SplitKey = ?RT:get_split_key(Key1, Key2, {1,2});
          false -> SplitKey = ?RT:get_split_key(Key2, Key1, {1,2})
      end,
      ?equals(histogram_rt:get_data(H3), [{SplitKey, 2}]),
      true.
  
  merge_keys(_Config) ->
      tester:test(?MODULE, prop_merge_keys, 3, 250, [{threads, 2}]).
  
negative.code:     SortedValues = lists:sort(fun(Val, Val2) ->
                                        nodelist:succ_ord_id(Val, Val2, BaseKey)
                                end, Values),
      %ct:pal("BaseKey: ~p SortedValues: ~p Result: ~p", [BaseKey, SortedValues, histogram_rt:get_data(H2)]),
      Result = lists:map(fun(Value) -> {Value, 1} end, SortedValues),
      ?compare(fun(Actual, Expected) -> check_result(Actual, Expected, BaseKey) end, histogram_rt:get_data(H2), Result),
      true.
  
  add_keys(_Config) ->
  