cant say that I've ever heard of that. I wonder if it would be hard to interpret test results with it being a liquid. I'm pretty skeptical...in my area I think just about anything could be passed off as "molly."
It has been a long time since 'Liquid' MDMA was available (and even then it wasn't that easy to buy/find). It's not actually liquid MDMA, its MDMA mixed with a liquid (usually alcohol).
I would NEVER buy it from a guy in an event as you have no idea what it is - when I hear of people saying they have liquid Ecstasy I automatically think of GHB GBL which is not something to mess about with (Especially if you have been consuming alcohol/other drugs etc).
Testing would work the same BUT even if it tested positive for MDMA / black I would still not touch it from some random guy at an event.