anchor.diff:  
       get_notified_by_message(2, [1,2,3,4], write),
       {ok, _} = write_via_node(2, "1", filter_list_append(), "TestWrite"),
  -    wait_until_notification(4),
  +    _= wait_until_notification(4),
   
       %% all replicas should have received the written value
       ?equals(prbr_values(), [[["TestWrite"]],
  
positive.code:     get_notified_by_message(1, 1, write),
      _ = slow_link(1, [2,3,4], write),
      spawn(fun() -> write_via_node(1, Key, filter_list_append(), "WriteA") end),
      wait_until_notification(4),
  
      %% read of client B
      _LinkB = slow_link(2, 1),
  
negative.code:                             [["TestWrite"]]]),
  
      remove_slow_link(Link),
      _= wait_until_notification(1),
  
      %% all replicas should have received the written value
      ?equals(prbr_values(), [[["TestWrite"]],
  