anchor.diff:  
   -required_variable(#{name => interarrival, value => 50, verification => positive_integer,
                        description => "a delay between creating the processes for two "
  -                                    "consecutive users (ms, def: 50ms)"}).
  +                                    "consecutive users (ms, def: 50ms)",
  +                     update => maybe_update_interarrival_timer}).
   
   -record(state, {scenario :: amoc:scenario() | undefined,
                   no_of_users = 0 :: user_count(),
  
positive.code:         Class:Exception:Stacktrace ->
              {error, {Class, Exception, Stacktrace}}
      end.
  
negative.code: %% ------------------------------------------------------------------
  %% Parameters verification functions
  %% ------------------------------------------------------------------
  -export([maybe_update_interarrival_timer/2,
           positive_integer/1]).
  
  %% ------------------------------------------------------------------
  %% gen_server Function Exports
  %% ------------------------------------------------------------------
  