Force India are the only team yet to confirm their 2019 driver lineup, although it is no secret that Mexican Sergio Perez will be joined by Stroll, whose billionaire father Lawrence took control of the team in August.
An announcement is expected later in the week.
The Canadian has already been replaced at Williams, who have an all-new lineup of Poland's Robert Kubica and Britain's Formula Two champion George Russell. All three were testing at Yas Marina.
The two-day test, following last Sunday's season-ending race at the circuit, allows teams to try out the 2019 Pirelli range of tyres.
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Kimi Raikkonen, the 2007 world champion, turned up as a Sauber driver for the first time in 17 years after wrapping up with Ferrari on Sunday. His running ended ahead of time when the car broke down.
Brazilian Pietro Fittipaldi, grandson of double world champion Emerson, had his first taste of a Formula One car with the U.S-owned Haas team that the 22-year-old has joined as an official test driver.
A technical problem sidelined him for much of the morning, however.
Formula Two runner-up Lando Norris was testing for McLaren ahead of the Briton's race debut next year, with Spaniard Carlos Sainz in the car on Wednesday after his move from Renault.
Charles Leclerc, Raikkonen's replacement at Ferrari, is due to test with the Italian team on Wednesday, when Pierre Gasly tests for Red Bull and Russian Daniil Kvyat makes his return to Toro Rosso.
(THis story has been refilled to correct Fittipaldi detail in seventh paragraph)
(Writing by Alan Baldwin in London; Editing by Hugh Lawson)
