Who really tests beauty products before using them?

Not me. And I have the equivalent of a bad sunburn on the lower half of my face to prove it.
Years ago, a friend of my mom's had a violent reaction to an inocuous beauty product -- lotion or moisturizer or sunscreen -- and ended up in the emergency room with hives and horribleness. My mom told me the story in warning over the phone, and I swear I could feel the whoosh! of her finger waving past me, even from a miles away.
I've had that stern voice in my head every time I've caught a glance of -- and ignored -- the warnings plastered to the sides of boxes of the many, many products I've slathered on my skin and hair and nails in the years since.
I really should do that 24-hour patch-test thingy, I tell myself guiltily.
And then I rip open the seventeen layers of plastic wrapping and glop it all over my parched/sensitive/super-fair/broken-out/petrie dish lab experiment skin.