anchor.diff:  t_4_test() ->
     Filename = "redbug.txt",
     Pid = spawn(fun()->receive P when is_pid(P)->P!ding;quit->ok end end),
  -  {_,_} = redbug:start('receive',[{procs,Pid},{print_file, Filename}]),
  +  {_,_} = redbug:start('receive',[{procs,Pid},{print_file,Filename}]),
     Pid ! pling,
     timer:sleep(100),
     redbug:stop(),
  
positive.code: 
  t_01_test() ->
    Filename = "redbug.txt",
    {_, _} = redbug:start("lists:sort", [{print_file,Filename},arity]),
    [1,2,3] = lists:sort([3,2,1]),
    timer:sleep(100),
    redbug:stop(),
  
negative.code: 
  t_0_test() ->
    Filename = "redbug.txt",
    {_,_} = redbug:start("lists:sort",[{print_file,Filename},print_msec]),
    [1,2,3] = lists:sort([3,2,1]),
    timer:sleep(100),
    redbug:stop(),
  