The tape test is used to determine if the leather or vinyl is able to receive a new finish after cleaning. See it demonstrated here at minute 2:28:
If painter’s or masking tape strongly adheres to the surface, such that you have to pry it off with a fingernail, you’re ready to proceed with restoration.
If the tape does not stick well or curls up at the corners, this indicates residue from silicone, wax or oil-based conditioning products, other cleaners, or body oil. This residue must be removed in order to get a durable finish. Clean the surface with denatured or rubbing alcohol and re-test until good adhesion is achieved. Acetone can also be used as a last resort with caution.
Tape does not adhere all that well to bonded or faux leather, and we do not recommend restoring these materials.