Cannabis testing device. Scam or what?

I recently took a few samples of my buds to a local grow shop that said they could test potency and terpenes with their new testing device. Well, my Purple Haze and Gold Leaf tested exactly e same which seemed unusual, but what really raised a red flag was my Blueberry CBD tested at 17.61% THC! The owner of the shop was as confused as I was, and did’n charge me the $40 for the CBD test. I did a little on-line research today on the MyDx testing device, and found that it may be a scam. I’m wondering if anyone else has experience or evidence that these test devices s actually work, or are they a scam?

Their reviews are pretty bad.
There is a good one on amazon that a few growers have. The name is tcheck 2. Pretty accurate.