The biggest retailer in the U.S., Walmart, is experimenting with robot shopping carts.

​The company has yet to release any details of how the robo-carts work. But ​the news highlights how rapidly automation is moving into shopping and warehouse fulfillment. It also shows how keen Walmart is to embrace any technology that might help it counter the shift toward online shopping and faster product delivery. Just a few weeks ago, Walmart also said it was testing whether drones could help check the inventory in its stores.

Robots have popped up in a few stores, mostly serving as experimental automated helpers. Behind the scenes, however, automation is rapidly taking hold at large retailers. Walmart’s archenemy, Amazon, has led the way by introducing automation to its fulfillment centers, using robots that ferry shelves stocked with products between stackers and pickers.

The space is becoming more crowded by the day. Other companies are developing robots capable of assisting with warehouse work in more sophisticated ways. In fact, last week I attended an event at which several other companies demonstrated other robotic warehouse helpers. NextShift Robotics, for example, showed a new system that can retrieve bins from shelves after workers have filled them with items. Another company, Locus Robotics, offers robots that can quickly be trained to move goods around a warehouse or factory.

All of which is to say that, while robot shopping carts might be a little unnecessary, it makes a lot of sense for Walmart to try to understand how automation may disrupt its business just as much as e-commerce already has.

(Read more: Bloomberg, New York Times, “Inside Amazon,” “Robots Are Invading Malls and Sidewalks Near You,” “A Dexterous Warehouse Robot Does Things Amazon’s Automated Helpers Can’t”)