Hair follicle drug testing?

I'm 17 and turn 18 next month..I wanted to apply to a Rite Aid where my parents both worked for the manager. I know they do pre-employment drug testing with a urine sample, but I am more worried about the hair drug testing..Does Rite Aid give hair testing to ALL their employees or is it just random like if your older and look like a drug addict? is there special stipulations on that..the last time i smoked marijuana was yesterday..and i hardly smoke and i know its gonna be in my hair but idk if they will take a hair sample..ANYONE THAT HAS WORKED AT RITE AID PLEASE TELL ME HOW THE DRUG PROCESS WORKS?