I'm low on time as I have to manage several projects so no promise on when Reactor.Core will do TCK. I merged in the environment support and have one test now that fails/hangs. It's kind of difficult to figure out why without the TCK sources at hand (which is neatly accessible in the JVM version).
Required_spec109_subscribeThrowNPEOnNullSubscriber : we don't throw ArgumentNullException but rely on NullReferenceException implicitly
Required_spec309_requestNegativeNumberMustSignalIllegalArgumentException : I guess it is expected request() calls onError but generally that's a concurrency violation on onError if the request() is asynchronous relative to onError
Required_spec309_requestZeroMustSignalIllegalArgumentException : same as above