Wow, I am so sloppy and unscientific when testing papers. I just print a negative that I kind of like which I know prints easily with a full range of tones. Generally I prefer to use a negative with more than the usual amount of contrast just so I can see how well the white and black print. If there's any fog, I throw in 2% Benzotriazole, a few millilitres at a time until the whites print cleanly. That's it. No quantifying level of fog; but I do keep note of how much Benzotriazole I've used for any particular paper and if the paper required more/less exposure than "usual" and more/less development.