I like Adam's "Turing test" a hell of a lot better than most of the Turing test concepts I've seen otherwise.
Alan Turing's idea isn't really sufficient, because it's very easy to trick a human being with machines, in part because humans are basically hardwired to imagine human traits everywhere. We see faces in grilled cheese sandwiches, we hear voices in the wind, we imagine human emotions and cognitive capabilities in animals that definitely have nothing of the sort.
But the thing we humans do that's borderline magic is a near instantaneous analysis of reality and ability to act on abstractions in ways that are almost too subtle to even describe -- accurately picking up on communication cues, body language, tiny bits of information, etc., and automatically altering or adjusting decisions on the fly factoring in that new information.
This video gets to one of the ways in which that ability manifests.