Lance Stroll enjoyed a 'secret' test between the recent Canadian and Azerbaijan grands prix.
After a lacklustre start to his rookie season, Williams's controversial rookie opened his points account in Montreal and was then on the podium at the end of the wild Baku race.
Germany's Auto Bild now reports that, in between those two races, 18-year-old Stroll got the benefit of a secret, private test in Williams's 2014 car at the US Grand Prix track in Austin.
When asked if the test gave his son a boost, Lance's billionaire backer and father Lawrence Stroll said: "To be honest, I don't think the test helped at all.
"It had also been planned for nine months. I think it's just time that has helped Lance.
"Every race, every lap that he turns, is a step forward. There are no real tests in Formula 1, so every grand prix is a test for him.
"It has never been so difficult for a rookie than this year, with these tyres and these cars."
The championship continues in Austria in two weeks' time.
