The toxic Agaricus californicus has a phenol odor, particularly in the base of the stalk--if you can smell phenol. I couldn't when I was younger, and in my late 20's, I ate an Agaricus californicus by mistake. I threw up for a couple hours, and have had a very good nose for phenol ever since. I don't recommend this method, however, if you can avoid it.
If you do chemical testing, all the toxic Agaricus sp., and the edible prince, turn yellow with KOH. The meadow mushroom doesn't turn any color, and the edible wine agaric turns greenish.