anchor.diff:                   fun(Bucket, Key, Value, Acc) ->
                            [{{Bucket, Key}, Value} | Acc]
                    end,
  -             ?assertEqual([{<<"b1">>, <<"k1">>}],
  +             ?assertEqual([{B1, K1}],
                             begin
                                 {ok, Keys} =
                                     Backend:fold_keys(FoldKeysFun,
  
positive.code:     }.
  
  fold_keys({Backend, State}) ->
      {"key folding test",
       fun() ->
               FoldKeysFun =
  
negative.code:                  end,
               FoldKeysFun3 =
                   fun(Bucket, Key, Acc) ->
                           case Bucket =:= B1 of
                               true ->
                                   Acc;
                               false ->
  