add 'assertTime' macro to eunit

[richcarl]

Luke Gorrie wrote on the erlang mailing list (06/11/2007 12:31 PM):

Did I ever post my favourite profiling macro? It's pretty simple:

-define(TIME(Tag,Expr),
    (fun() ->
             %% NOTE: timer:tc/4 does an annoying 'catch' so we
             %% need to wrap the result in 'ok' to be able to
             %% detect an unhandled exception.
             {__TIME, __RESULT} = timer:tc(erlang,apply,[fun() -> {ok,Expr} end,[]]),
             io:format("time(~s): ~18.3fms ~999p~n", [?MODULE,__TIME/1000, Tag]),
             case __RESULT of
                 {ok,_} -> element(2, __RESULT);
                 {'EXIT',Error}  -> exit(Error)
             end
     end)()).

if you wrap it around a few strategic expressions in your code you end
up with simple running-time summary printouts like this:
time(backup): 3654.744ms restore_table_defs
time(backup): 182.969ms restore_secondary_indexes
time(backup): 311.973ms restore_records
time(backup): 20.928ms checkpoint
time(backup): 5.095ms remove_logs

Update1: Added a macro ?debugTime(Str,Expr) to eunit.hrl in revision 257 (​https://forge.process-one.net/changelog/P1Contribs/trunk/eunit?cs=257), inspired by the one by Luke.

Update 2:
In what way does this differ from timeouts?
Simply measure wall clock before and after?
Use non-hardware dependent units with automatic calibration á la bogomips? (berps?)
Have different macros for measuring different things?
Macros for checking linear/quadratic/exponential time?