What is the definition or description of: reality testing?

Ego Function: In psychoanalytic theory, the ego function by which the objective or real world and one's relationship to it are evaluated and appreciated by the self.

Reality testing: A reality test is something you do to help yourself come to grips with reality. When you have paranoid/delusional ideations, you have to do reality testing to help remind you of what is truly real and what is all in your mind. For example if you hear voices telling you demeaning comments or that you can fly and that you be best left in a dark corner and you belief these thought to be true.

What is real?: The crucial ability to distinguish thoughts, feelings & perceptions (internal stimuli) from what is going on around you (external stimuli). Delusions, severe anxiety, or hallucinations may make reality testing difficult. Example: you might get on the bus & feel others are looking at you, plotting against you. "i'm just thinking that, it's not really true" might indicate good reality testing.