anchor.diff:    {ok, <<"a">>, _RevId2} = barrel_local:delete(<<"testdb">>, <<"a">>, RevId2, []),
     {error, not_found} = barrel_local:get(<<"testdb">>, <<"a">>, []),
     {ok, <<"a">>, _RevId3} = barrel_local:put(<<"testdb">>, Doc, []).
  +
  +
  +revision_conflict(_Config) ->
  +  Doc = #{ <<"id">> => <<"a">>, <<"v">> => 1},
  +  {ok, _, _} = barrel_local:put(<<"testdb">>, Doc, []),
  +  {ok, Doc1} = barrel_local:get(<<"testdb">>, <<"a">>, []),
  +  Doc2 = Doc1#{ <<"v">> => 2 },
  +  {ok, <<"a">>, _RevId} = barrel_local:put(<<"testdb">>, Doc2, []),
  +  {conflict, revision_conflict} = barrel_local:put(<<"testdb">>, Doc2, []),
  +  ok.
   
   
   async_update(_Config) ->
  
positive.code: -export([
    basic_op/1,
    update_doc/1,
   async_update/1,
    bad_doc/1,
    create_doc/1,
    docs_count/1,
  
negative.code:     basic_op,
      update_doc,
      async_update,
      revision_conflict,
      bad_doc,
      create_doc,
      docs_count,
  