Someone mentioned energy control above i was trying to remember the name of them initially but yeah as per noted they will only tell you what substances are in there i believe not the amounts. But they are an option for ruling out adulterants. I may be wrong about wendinos but its a paid service unlike EC which (i believe?) only costs u postage so i presume theres more detailed analysis involved.
Many organisations such as dancesafe, the loop, and local HR initiatives get these tested by similar companies (or own their own mass spectrometer), and post reports. Also vendors will claim mdma content of pills but this is an average over the batch (if we assume it isnt exaggerated) and clandestine mixing is shitty at best so you can have massively varied results. I saw a pillerport with 2x 2cb pills from the same batch with something like an 800% difference in active content lmao. The general consensus at the moment is if your pills came from netherlands/youre in europe, they are higher strength 200-300mg, sometimes in excess of that, so start with a quarter and drink water

The reason for this is their laws chjarge based on number of ecstasy pills rather than total mdma content of the pills when it comes to constituting possession vs intent to supply. Overseas its different (i in the UK and we pretty much get either really strong mdma content pills, or ephylone lol) and theres more varied quantities and meth starts to become apparent as a cut when u talk about the states or Oz.
Also reagents are not 100% effective anyway, but less so with MDMA. MDMA has such a dark reaction, that the deep colours overpower the reaction of potential adulterants mixed in. IIRC you cant know if you have an apb (or is it abp? "benzofury" in any regard) analog for certain if theres also mdma in there. Cathinones, including the currently notorious n-ethylnorpentylone are all a light yellow on marquis so the purple overshadows that.
Also having taken a lot of mdma in my time if we assume average purity of the crystal itself, i can spot when iv had more than 125mg a mile off. Iv been weighing almost all my doses for so many years now that iv gotten very good read on the dose response *subjectively speaking*. But id never claim to "know" what was in a pill. Just whether or not half of one still exceeds my usual range. Harder to tell when its slightly under.