Again you Seem to have little knowledge about the subject when you keep mentioning tablets.. mdma usally comes in crystal form and has a distinct taste. Ecstasy is a whole other thing usally containg amfetamine, ketamin and many other things.
This is all very poor advice.
Get chemical test kits, use drug testing services where they are available, be cautious.
Which is pretty terrible itself, powders and crystals can be just as adulterated as pills. Relying on sight and taste to tell what you've got is very unreliable.