"Luck" or "intelligence"? How do you tell the difference from a distance?

Recording predictions and comparing them to actual events helps.

It's not guaranteed -- it's still possible that my predictions came true by sheer coincidence -- but the amount of luck required to fulfill detailed predictions is significantly higher than the amount of luck required to support compelling post-hoc explanations.

Of course, this presumes that the putatively intelligent system is attempting to demonstrate it's intelligence. If they want me to think it's luck, that's a much harder problem.