A girl was looking for marijuana test strips as well.
Girl: Do you know about the sensivity of the test?
Pharmacist: No, we don't.
I walk past trying to get to another customers.
Girl: You don't either, do you?
Me: No. *First time in history a customer turned to me while speaking to my pharmacist*
The girl read the leaflets and discovered that the test strip changes color depending on the concentration detected.
My guess is - she is trying to get away with smoking marijuana. A little does not harm as long as it goes undetected. Always wrong but only guilty when you are caught.