They can be finicky, and sometimes give false negatives when you miss tight time windows on color changes and matching. They certainly aren't as good as sending it to a lab, but if you get a positive test from them, you can be fairly certain it is legit.
we have seen the past couple years social media guys selling them on their websites and they have been proven to be innacurate. if you get a legit test then yes they will be accurate if you test correctly. most of the ones you get online though i would not trust at all.