Fingernail test? wow,thats advanced, like a hair test I presume,as In the ganja you somked stays in your hair, so I take it thats the same as fingernails. Maybe cut your fingernails now so in a week there grow back clean. this would mean that you have to not smoke once you have cilpped your finger nails.
so if you cut your nails,and dont have any white they can use,,(I take it thats the bit they use) then theyd cause you pain to cut the pinky bit. so they couldnt do it. and if you dnt wash you feet they wont want to go near them for toe nails.
good luck to you.