You order a unit to cast a spell it hasn't learned yet, what happens?

If I tell a unit to Human Paladin - Holy Light xxxx and it doesn't know the holy light spell (whether custom or not) will the unit sill cast the spell, or will the trigger not acitvate? OR will the game crash? (gasp)

TEST EVERYTHING FFS DON'T ASK FOR SO STUPID THINGS YOU CAN TEST YOURSELF...

most likely nothing will happen...

Yeah, you could have gotten a quicker answer by trying it for yourself.
But nothing happens, the order does nothing.

wow... Jeez Jacek calm down. Thx anyways.

If you order to Human Paladin - Holy Light, and it hasent learned it, but another spell has the same Order String, then it will cast that.
Human Paladin - Holy Light is just a GUI saying of the orderstring.