Williams has confirmed that Formula E world champion Nyck de Vries will replace Alex Albon for first practice at the Spanish Grand Prix.
As part of a new rule introduced this year, all 10 teams are required to run a 'rookie driver' in two FP1 sessions across the season.
To avoid doubt, a rookie is classified as a driver who “may not have participated in more than two F1 World Championship Races during their career”.
Alongside his Formula E team-mate Stoffel Vandoorne, de Vries serves as a Mercedes F1 reserve driver.
The Dutchman has previously tested for the Silver Arrows, including at last year's end of season test in Abu Dhabi, but his outing with Williams will be his first in an official session.
"Firstly, I’d really like to thank Williams for the opportunity to run in FP1," said de Vries.
"It’s great for me to get to know the team and drive the FW44, and also to get myself out on track during a Formula One weekend.
"Preparation for the test is going well so far and the team have been incredibly supportive of me. I’m very much looking forward to the whole experience in Spain now!"
Williams eager for de Vries input
De Vries will arrive in Spain fresh off the back of a victory at the Berlin E-Prix, his second success of the year for Mercedes.
Williams head of vehicle performance, Dave Robson, added: "We are looking forward to having Nyck de Vries in the car for FP1 as it is always good to work with a new driver and get a fresh opinion on the car's strengths and weaknesses.
"Nyck's experience and professionalism will be crucial on Friday as he will complete some of the key engineering tests in FP1 before he hands the car back to Alex for FP2."