Wasted a whole day on a bad coolant test strip kit

You know what, maybe the strips get a bad rap. I mean, did you check the expiration date on that box? I've used them for years on my own cars and never had a problem. Could be you just got a bad batch or they got left in a hot truck or something. A refractometer is overkill for most people just trying to see if they need a flush. Those strips are cheap and fast, and they work fine if you buy them from a place that sells a lot of them so the stock is fresh.