The lie of Santa Claus may be a learning experience, but it isn't actually a test per se -- every child finds out the truth one way or another.

What about ghosts, the supernatural and everything else of that kind they'll encounter in movies, television, cartoons, etc? The only difference with Santa is that most people grow out of it, whereas many adults continue to believe in ghosts, but that's because Santa is childhood-specific myth. If the same adults who think Santa is absurd were supposed to believe in Santa I'm sure they'd have no problems rationalizing it.