There are several reliable sdcard test utilities to verify capacity.
True, and it is a great idea for the typical user. I am primarily worried about speed and reliability for my cameras. The tests can show speed but not reliability. For work, we purchase fixed BOM industrial grade SLC memory cards that are good for millions of read/write cycles. Your typical consumer cards are MLC cards which are usually only good for 200,000 or so writes. 200,000 sounds like a lot, but when you look at how often the FAT table is updated you can start wearing a card out quickly. Better consumer grade cards do employ wear-leveling to extend the card's life.
For my cameras, I go with the best card I can afford. I have been looking at dashcams lately. I would think a dashcam could wear out a consumer grade card in a year or two in a daily driver. A counterfeit card in probably less time. Seems a good consumer grade card is a good compromise if it isn't a counterfeit.
OK, I think I have had too much coffee this morning.