anchor.diff:      {ok, pid()}.
   start_link(Scenario, Id, State) ->
       proc_lib:start_link(?MODULE, init, [self(), Scenario, Id, State]).
  +
  +stop() -> throw(normal_user_stop).
   
   -spec init(pid(), amoc:scenario(), amoc_scenario:user_id(), state()) ->
       no_return().
  
positive.code: -module(amoc_user).
  
  %% defaults
  -define(REPEAT_INTERVAL, 60000). % time between sceanario restarts (60s)
  -define(REPEAT_NUM, infinity). % number of scenario repetitions
  
  %% API
  -export([start_link/3]).
  -export([init/4]).
  
  -type state() :: term().
  
negative.code: -spec flush_mailbox() -> ok.
  flush_mailbox() ->
      receive
          _ ->
              flush_mailbox()
      after 0 ->
  