The online reservation service OpenTable is set to begin letting diners pay for meals through its app.

Matthew Roberts, CEO of the San Francisco-based company, the world's largest online reservation service, tells The New York Times that the service, still in testing, will be straightforward. At the end of their meal, diners would open the OpenTable app and pay with the touch of a button.

OpenTable recently acquired JustChalo, a mobile technology company working on a payments application for restaurants. Roberts said JustChalo is testing the payment system in 20 restaurants, and he expects OpenTable to introduce the system in San Francisco by the end of the year and to expand from there.

Learn more about mobile payments and restaurants.