Psychological testing measures an individual’s performance at a specific point in time — right now. Psychologists talk about a person’s “present functioning” in terms of their test data. Therefore psychological tests can’t predict future or innate potential.
Psychological testing is not a single test or even a single type of test. It encompasses a whole body of dozens of research-backed tests and procedures of assessing specific aspects of a person’s psychological makeup. Some tests are used to determine IQ, others are used for personality, and still others for something else.