This week Peapod by Giant started testing a grocery delivery service at three D.C.-area Metro stations: Fort Totten, Glenmont and Vienna. Shoppers can order their groceries online, then pick them up as they exit the Metro between 4 and 7 p.m. Mondays, Wednesday and Fridays. The three participating stations have lockers to store the groceries and staffers available to help shoppers to their cars. If things go well with this six-month test, more stations will be added to the program.