When an illegal drug crew gets a new shipment and/or a new supplier, it is not uncommon for them to have one day where they give out "testers", essentially free samples that junkies will ultimately comment on the quality of. It ensures the dealers or not being ripped off by suppliers and can also cause some junkies to become loyal to that crew and their product. Junkies are often very excited for tester day, since it means a rare free high.
C'mon, we gotta get down to 53rd! The Felson crew is putting out testers today!