Sauber announced in July that it planned to prepare the 18-year-old for a race seat, subject to him gaining a Superlicence.
But even though there would be time for Sirotkin to complete the required mileage during pre-season testing, the team has instead signed Adrian Sutil and Esteban Gutierrez and will continue to prepare Sirotkin for a race seat in the long-term.
"We have been working with Sergey since August, and he has been able to gain more and more insight into Formula 1," said Sauber team principal Monisha Kaltenborn.
"Now he is taking the next step towards the top level of motorsport in his new role as test driver.
"Our experience of him is as a very focused, calm, and talented driver.
"Now we will continue to support him, including obtaining his Superlicence. Our goal remains to prepare him for a debut in Formula 1."
Sirotkin was given mileage in a 2009 Ferrari F1 car at Fiorano and drove a 2013 Sauber in a demo run using part of the Sochi circuit as part of his preparations.
But he also continued to run in Formula Renault 3.5 machinery in post-season testing for both the ISR team, which he raced for in 2013, and Fortec Motorsports.
It is not clear whether he will get any F1 mileage in 2014, but should Sauber want to ensure he gains a Superlicence he will need to be given some time in the car.
"It's a big chance for me to become the test driver for the Sauber F1 team," said Sirotkin.
"I will work hard to improve myself and to extract the maximum out of this opportunity.
"Formula 1 is very complex, so it is important to get an opportunity like this.
"My main focus next year, however, will be the World Series by Renault, which is very competitive.
"This will give me the chance to prepare even better in order to be ready for the next big step."
- Sports & Recreation
- Motor Racing
- Adrian Sutil
- Esteban Gutierrez
- Sauber F1 team