The online grocery business is small-scale right now, but the potential for growth just got a lot better: Walmart is taking a stab at it. The chain announced it is testing a "Walmart To Go" service in San Jose, California, reports Reuters. Customers can order groceries from the store website and have them delivered. Low profit margins and the logistics of dealing in perishables have kept such services from going mainstream, analysts say. (More Walmart stories.)