I'm happy with the 4 bottle" E-Z Test " www.ez-test.com It's saved me many times. I always bring it with me, first I ask what logo's on the pill and go to Pillreports.com and find out what I could about a pill in my area. I once hooked up with this (old friend) for a large buy, these were a dark green bean with an "E" on the front. Well the e-z- test were blank and I passed on them only to find out they were dyed excedrin tabs !!!Same goes for gelcaps I hardly ever find any with mdma.
i reckon it depends on what the common adulterants are in your area.
so if ketamine is a problem then get a test which shows its presence for example mandelin.
but to be totally as safe as possible ( nothing is 100% safely going to say what is exactly in that pills excepts expensive lab equipment) probably the ez-test extreme.