Bookwyrm627: What are you attacking? What stage of the game? Which weapons and spells did you use?
angelgt1980: Still in the academy, so basically it's combat dummy.. I've tried with weapons in the "combat" room and with spells in the "magic" room in order to pass the test, but nothing happens and I have no idea why all my attacks are ineffective..
What weapon? If you fight the instructor, which is the alternative min-quest (task, really) solution, he takes no damage. This task with the combat dummy is meant to test advanced combat tactics, like
Power Attack, which are meant to be selected from the radial menu. The test also allows you to, instead, try attacking the guard teacher, using another technique,
Parry. If you aren't using such techniques, it won't trigger the successful completion.
Are you a mage class? I'm not sure if you can destroy the targets in the magic room without magic. Ditto for divine magic against the skeleton in that room.
This is all in the dialog text, which explains it. Re-read it to discover what you missed. (You've read more in this topic.)