Sirotkin, who lost any hope of being retained by Williams for 2019 when the Grove squad announced Robert Kubica as its second driver last month, is currently present for the Jerez test that started on Monday and finishes on Wednesday.

The Russian driver was included on a list of seven drivers tweeted by Audi on Monday evening, along with five of the six drivers the German marque initially announced two weeks ago.

He will be at the wheel of one of Audi's two 2018-spec cars at Jerez, one of which is being run by new customer team WRT.

Formula 3 driver Sacha Fenestraz is the other late addition to the Audi line-up, replacing Carlin teammate Ferdinand Habsburg, who was chosen as one of four Mercedes drivers for the test.