If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck. The test implies that a person can identify an unknown subject by observing that subject's habitual characteristics.
You might think being alone makes you lonely, but that*s not entirely true. Being surrounded by the wrong people is the loneliest place in the world. Before you diagnose yourself as an unhappy person, first be sure that you are not simply surrounded by negative people constantly trying to bring you down to their level.