There are a few different venues that give HIT's and then there are some dog people with farms who have fun days to give non certified HIT's. Where are you located I might be able to find one for you tho I can't promise anything. Most tests that I've been to just involve the dog going into a "take pen" with 3-5 sheep and moving the sheep in circles. The only purpose is to see if the dog stays engaged and see if they have any natural wearing or balancing behaviors. Some new highly aroused dogs may even bite at the stock(as long as it's with excitement and not fear that's ok) and may cut the group.
My experience comes from the Aussie side of things however and I think Border Collie people give very different HIT's because Border Collies are a natural distance worker and Aussies are natural close worker. The take pen may not be conducive to properly assessing a BC as it is for an Aussie.