How is the fire test for dry chemical fire extinguishers conducted?

Your question wasn't really clear but I'm assuming you mean how do you test a dry chemical fire extinguisher at home. Normally these types of extinguishers are tested at home by simply turning them upside down and listening to them to make sure the dry powder hasn't started to cake in the bottom. If you hear the sound and the gauge on the top of the bottle shows in the "green" the extinguisher is fine. Don't try to test them by pulling the trigger and seeing if they shoot, there's not a heck of a lot of powder in there to play around with.