These EZ Test MDMA purity tests worked well.
Pill results approximately matched drugsdata.com reported lab values. The color indicated that the pill was approx 50% MDMA by weight (a bit less, maybe 45%), and saferparty.ch lab result showed approximately the same concentration (45-50%). So you know your pill is (probably) not a fake)
Test of a crystal sample was noticeably darker (80%+). Using the printed color chart, it looked closer to 75-80%. But using the following photo of actual test tubes, it's closer to 100. As stated above, this is MDMA*HCl, so 97+ is possible (but rare!)
This pic helps a lot (easier to compare than the printed color chart that comes with the test).
Use something like a folded playing card, or a folded hotel room card to groove 20mg into the tube without it sticking. Guide it in with a needle or tweezers.
(First put the card on the scale. Then add sample, so the total weight is 0.02g higher. Don't zero (tare) your scale, hurts accuracy).
For $30 you can get an adequate 0-20g scale at 0.001 g.
Take pictures with your phone at 5, 15 and especially at 45 minutes, (so you can compare the color to other pills / samples you may need to test a year later)
The little test vial can stand on the table by itself, but it's easy to tip it over, esp since you need both hands to add the sample. So, before you get started, find some kind of steady holder / stand for that little test vial.
You need bright daylight and a white background.
Hope this was helpful. I don't work for them. Just a noob myself