anchor.diff:  
   madd_binary(Conf) ->
       Keys = keys(Conf),
  -    madd(cluster_binary, cluster_txt, Keys).
  +    madd(cluster_binary, cluster_txt, Keys),
  +    madd_moving(cluster_binary, cluster_txt, Keys).
   
   mset_binary(Conf) ->
       Keys = keys(Conf),
  
positive.code:          %% mincrement_binary,
           %% mincrement_txt,
           %% cas_binary,
           %% cas_txt
           %% mgets_binary
           %% madd_binary,
           %% mset_binary,
           %% mcas_binary
  
negative.code:     ?assertEqual({hd(Keys), <<"xyzzy">>}, mero:get(Cluster, hd(Keys), 1000)).
  
  
  madd_moving(Cluster, _ClusterAlt, _Keys) ->
      %% with one existing key, add new keys repeatedly, moving the
      %% position of the existing key each time:
      ExistingKey = key(),
      MakeKeys = fun (Start, Count) ->
                         [<<"key", (integer_to_binary(I))/binary>>
                          || I <- lists:seq(Start, Start + Count - 1)]
                 end,
      Total = 100,
      lists:foreach(fun ({Start, N}) ->
                            mero:flush_all(Cluster),
                            ok = mero:add(Cluster, ExistingKey, ExistingKey, 1000, 1000),
                            CurKeys = MakeKeys(Start, N)
                                ++ [ExistingKey]
                                ++ MakeKeys(Start + N + 1, Total - N - 1),
                            ExpectedResult = [case Key of
                                                  ExistingKey -> {error, already_exists};
                                                  _ -> ok
                                              end
                                              || Key <- CurKeys],
                            ?assertEqual(ExpectedResult,
                                         mero:madd(Cluster, [{Key, Key, 1000}
                                                             || Key <- CurKeys], 1000)),
                            ?assertEqual(lists:keysort(1, [{Key, Key}
                                                           || Key <- CurKeys]),
                                         lists:keysort(1, mero:mget(Cluster, CurKeys, 1000)))
                    end,
                    [{1, N}
                     || N <- lists:seq(1, Total - 1)]).
  
  
  mset(Cluster, _ClusterAlt, Keys) ->
      KVs = [{Key, Key, 1000}
             || Key <- Keys],
  