The two most common tests are the LD50 test and the Draize
test.
In the LD50 test, which tests how toxic something is, a group of
animals is forced into a small corral along with a toxic substance
and a timer is started to see how long it taked for 50% of the
animals to die.
The Draize test tests how irritating something it using rabbits.
Rabbits eyes are clipped open and a substance is forced into them
and irritation is measured.