I to have also been guilty in the past of doing this! Believe it or not there is a right and wrong way in testing your makeup. Your face is most times lighter than the rest of your body because we're constantly shielding it from the sun with spf and foundation. Your arm or hand should be the last place you test your foundation on your body. Next time you take a trip to the drugstore to buy new or your usual foundation only test on your neck! You'll definitely see the difference. Happy Shopping!