Paul di Resta and Robert Kubica are set to test a 2014 Williams car at the Hungaroring later this month, according to Motorsport Magazine.
Whoever impresses the most will be chosen to replace Felipe Massa at for the 2018 season alongside teammate Lance Stroll.
The original plan was to have Kubica run a test in a 2014 car in Suzuka between the Singapore and Malaysian Grand Prix, however, it was scuppered when Stroll, for whom that car is specifically run, objected to having used for testing another driver.
Stroll's objections left Williams scrambling to find a replacement test car for Kubica, a driver who, following an injury to his right arm in 2011, never looked like returning to Formula 1.
Kubica's performance will be measured against Brit Di Resta, who has the reserve driver for Williams in 2017 and surprised many with a strong performance filling in for a sick Felipe Massa at the Hungarian Grand Prix.
That performance seems to have reversed the fortunes of Di Resta, who was cut from Force India in 2014 after a series of poor races.
Both drivers have a lot to lose and as much to prove in this upcoming test. In their 30's, both bring the experience and drive necessary to perform well, although they may also be nearing the end of their prime.
There also remains the slim possibility Felipe Massa could continue for a fourth season.The Brazilian has performed well after reversing his decision to retire at the end of last year.
Nevertheless, Williams desire to test both Di Resta and Kubica suggests the manufacturers would prefer to shake up their line up for the new campaign.