Nope! Reagent tests can only indicate that you do not have a certain compound; they can't definitely confirm an identity. If you really want to know, send it in to ecstasydata for mass spec.
^ Untrue, if you have the FULL regent test you can usually find out the exact identity of any substance
the marquis will only give you an idea, based on the chemical structure of the compound though. IE: MDMA, MDA, MDE, and all other MDxx drugs will turn it purple/black. Meth, amphetamine and other versions of it will turn brownish/yellow/orange, substituted cathinones like methylone will turn it neon yellow, and 2C-X will turn it varying shades of green