TuSimple, the self-driving truck startup that reached unicorn status earlier this year with a $1 billion valuation, is getting two weeks to prove its tech to the United States Postal Service.

The company announced Tuesday that it was awarded a contract to complete five round trips, for a two-week pilot, hauling USPS trailers more than 1,000 miles between the postal service’s Phoenix and Dallas distribution centers. A safety engineer and driver will be on board throughout the pilot.

TuSimple will run a series of its self-driving trucks for 22 hours each, which includes overnight driving, along Interstates 10, 20 and 30 corridors to make the trip through Arizona, New Mexico and Texas.

The pilot is an important milestone for TuSimple. It marks the company’s first foray into Texas; it’s also a chance for TuSimple to validate its system with the U.S. government.

The USPS is just one of many (ahem Amazon) in the logistics and shipping business interested in using autonomous vehicle technology to cuts costs and improve safety and operations.

TuSimple, which launched in 2015 and has operations in San Diego and Tucson, Ariz., has been running daily routes for customers in Arizona. The company recently raised $95 million in a Series D funding round led by Sina Corp. The company is preparing to scale up its commercial autonomous fleet to more than 50 trucks by June.

TuSimple has raised $178 million to date in rounds that have included backers such as Nvidia and ZP Capital. Sina, operator of China’s biggest microblogging site Weibo, is one of TuSimple’s earliest investors.