Facebook on Wednesday unveiled insights into how it tests new code on thousands of mobile devices at an until-now secret lab in its Prineville, Ore., data center.The social networking company also said it plans to open source the hardware design used in its custom mobile device testing rack as well as Chef software. which is used to control smartphones and other devices for the testing operation.clouds 616122 1920Master Class: 3 ways to fast-track your journey to the cloud (with podcast and video)Listen, watch and learn as FCC CIO David Bray explains how to leverage change agents when pivoting toRead NowIn a lengthy blog post, Facebook production engineer Antoine Reversat laid out how the testing lab helps engineers monitor the way thousands of code changes each week can affect a smartphone’s memory, data or battery usage.The blog describes an elaborate process of building up the lab to test nearly 2,000 phones on different operating systems and networks and with different configurations.The work started last year when Facebook created a CT-Scan service, which monitors and predicts the implications of code changes, but that approach didn’t scale to enough devices. A small team of engineers was created to tackle the problem. The group quickly decided not to use a simulator approach, preferring to test code changes on actual devices for greater accuracy.Managing the sheer volume of devices that needed to be tested involved issues, including making sure Wi-Fi would work properly with each device. The engineers moved from various approaches starting with a “sled” design, then the “gondola” design, then a “slatwall” and finally a custom-built “rack” that resembles a traditional server rack on the outside with dozens of phones connected inside. Facebook said it will open source the design for the custom rack, but didn’t announce timing.