Do attacks by hallucinations trigger an "our forces are under attack" message?

Basically, I want to know if I can effectively fake some harassment with a force made entirely of hallucinations.

For example, I could fake harassment of one base to draw forces away from the base I actually want to attack. But I want to make sure that to the opponent, it appears to be a normal attack (except that they take no damage, of course).

Yes, they will appear as normal attacks with that warning and everything, but it will be very obvious that they're not doing any damage so I don't think an all-hallucination army would be very effective use of sentry's energy.

If you mix real units in, then it's much harder to tell if they are hallucinations or not.