It has never been an issue for me as I don't partake, but anecdotally, I've worked at 5-10 mid range (100-200) firms in Virginia and Illinois and while I have been provided many free beers at work, if anyone suggested a drug testing program they would have been laughed out of the building.
I even worked for a company that ran drug testing programs for the government and they did not drug test.
I even worked for a company that ran drug testing programs for the government and they did not drug test.