If you have a NextDoor app or similar service in your area, this might be a good question for there. That way if you eventually need a testing lab, you can get a local recommendation.

A test kit should be a container and instructions for mailing it to a lab. It's really just a sample collection and shipping kit. Assuming the lab is a good one - and they should be certified for asbestos work, ask them if it's not clear - the results should be accurate.

If all you'll be testing is the popcorn ceiling, no real need to have a professional come out and charge you a lot of money. If there is no local lab, a test kit should be fine.

A reliable test needs to be done by a certified asbestos testing lab. Your state or local pollution control organization should have a list of accredited labs. You bring or send a small sample to the test lab and they perform a special kind of microscopic inspection to examine for fibers that are characteristic of asbestos. It should also not be very expensive: a reasonable price to expect would be no more than $100.

Also, it's very important to hang onto those test results and file them in their own folder that stays with the house if/when you move. You think you'll remember in 10 years, but you won't, and it will also save future homeowners a hassle and expense. Not to mention that when you sell, you can tell them definitively whether it's ACM or not.