What is the X in X-mas?
aptitude test ap·ti·tude test (āp'tĭ-tōōd', -tyōōd')
An occupation-oriented test for evaluating intelligence, achievement, and interest.
examination that attempts to determine and measure a person's ability to acquire, through future training, some specific set of skills (intellectual, motor, and so on). The tests assume that people differ in their special abilities and that these differences can be useful in predicting future achievements.