anchor.diff:      {ok, L2} = update(DownstreamOp1, L1),
       ?assertMatch([{ok, 1, _}, {ok, 2, _}], L2).
   
  -%% In the tests that follow, the values of generate_downstream are placed by hand so
  +%% In the tests that follow, the values of generate_downstream are placed by hand ,so
   %% the intended scenarios can be correctly tested, not depending on the unique() function.
   
   insert_in_the_middle_test() ->
  
positive.code: %% first call `generate_downstream/3', to get the downstream version of the
  %% operation, and then call `update/2'.
  %%
  %% It provides two operations: insert, which adds an element to the RGA, and delete,
  %% which removes an element from the RGA.
  %%
  %% This implementation is based on the paper cited below.
  
negative.code:     {ok, L5} = update(DownstreamOp5, L4),
      ?assertMatch([{ok, 1, _}, {deleted, 2, _}, {ok, 4, _}, {ok, 3, _}], L5).
  
  purge_tombstones_test() ->
      L = new(),
      DownstreamOp1 = {addRight, {ok, 0, 0}, {ok, 1, 1}},
      DownstreamOp2 = {addRight, {ok, 1, 1}, {ok, 3, 2}},
  