To Do
=====

- Let the test pass when it's known that it will file. Similar to isnt() in Test::More
  The basis fir this is in command_validation.t because with the current implementation
  can't simple say "it's OK that run_ok fails !!!" or for anything else.

- use -n switch for some shells that allow syntax checking
  Thanks Matias Palomec from CaFe PM (http://cafe.pm.org)

- use -x switch to generate testing output 
  (http://www.cyberciti.biz/tips/debugging-shell-script.html)