Robert Kubica and Paul di Resta are set to take part in two one-day tests with Williams to evaluate both drivers over a possible 2018 seat with the team.
The pair are understood to be in direct competition with Felipe Massa over his seat at Williams, with the Grove-based outfit keen to assess which driver of the three should partner Lance Stroll next year.
Williams plans to run both Kubica and di Resta in a one day test at Silverstone on October 11 in a 2014-spec F1 car, before a further test is carried out at the Hungaroring a few days later on October 18.