anchor.diff:                    slide:mean(S3, 9, 10)),
       S3b = idle_time_passing(S3, 6, 13),
       S4 = slide:update(S3b, 11, 14),
  -    ?assertEqual(23/11, % ignoring first reading, avg = 
  +    ?assertEqual(23/11, % ignoring first reading, avg =
                    element(2, slide:mean(S4, 14, 10))),
       S4b = idle_time_passing(S4, 15, 18),
       ?assertEqual(11/10, % shifted window
  
positive.code:     Reading = if Reading0 < 4000000000 -> Reading0;
                   true                  -> 4000000000
                end,
      %% 4 bytes len header + 8 bytes ... 
      Bin = pad_bin(term_to_binary(Reading), 8),
      ok = file:write(S1#slide.readings_fh, [<<8:32>>, Bin]),
      S1.
  
negative.code:     S5 = slide:update(S4c, 13, 22),
      ?assertEqual(24/10, % shifted window
                   element(2, slide:mean(S5, 22, 10))).
  
  mean_and_nines_test() ->
      setup_eunit_proc_dict(),
      PushReadings = fun(S, Readings) ->
  