The character or characters are undergoing some special training, usually military in nature. During a critical evaluation or test (often the "final exam" for the program they are in) something goes horribly wrong, and they find themselves alone and in hostile territory (or a disaster situation). Without their instructor(s) or any hope of help from their command structure, they must fight or finagle their way to a point where they can be rescued. When they make it, they discover that the entire experience -- complete with the accident that set the disaster in motion -- was the exam, planned and staged completely in order to see what their response would be to a real crisis or combat situation. Sometimes it's intended to weed out the unfit members of the class as well.