anchor.diff:  
       ?assertMatch({error, {function_clause, _Detail}}, Result),
   
  -    stop().
  +    {ok, stopped} = stop().
   
   never_die_test() ->
       {ok, Pid} = start(),
  
positive.code: 
      ?assertEqual({ok, 52.27433388230814}, Result),
  
      stop().
  
  stop_test() ->
      {ok, Pid} = start(),
  
      {ok, stopped} = stop(),
  
      receive after 10 -> ok end,
      ?assertNot(is_process_alive(Pid)),
  
      stop().
  
  sum_unknown_areas_test() ->
      {ok, _Pid} = start(),
  
negative.code: 
      ?assert(is_process_alive(whereis(?math_server))),
  
      {ok, stopped} = stop().
  
  start_consecuative_twice_test() ->
      {ok, _Pid} = start(),
  
      {error, already_started} = start(),
  
      {ok, stopped} = stop().
  