Canada's drug testing rights policies??

I want to get a job where i don't have to be tested or worry about loosing my job from a failed marijuana test

I am going to school for engineering, and am wondering if anyone knows the privacy rights and stuff like that about company drug testing in canada. I was considering looking for a job there and residing there once i have a job....if...i am safe from drug testing by employers

I currently live in the U.S. Do you think i'll be safe staying and living here without much testing?

anyone have any knowledge???