extending form_validation

[eluser]tomcode[/eluser]
1. I have my extending libraries under application/libraries, never tried having them in the system
2. the file name should be MY_Form_validation.php, not MY_form_validation.php
3. put a log message in the constructor of MY_Form_validation, them You're sure whether the file is loaded
4. the method test_my_function() should take one parameter (the value to validate), i.e. test_my_function($value)