Japan's Kazuki Nakajima will race for Williams next season, the Formula One team confirmed on Wednesday.
The Indian F1 ace said being a test driver will boost his reputation.
The Australian will take the place of young Austrian Christian Klien at the team.
Austrian test driver Alexander Wurz will replace Mark Webber in the Williams race line-up next season.
The Australian would be favourite to replace Alonso at Renault if the world champions fail to secure Kimi Raikkonen from McLaren.
Wurz, 31, has been a McLaren tester for the last five seasons after racing for Benetton from 1997 to 2000.
The MP4-18 made its first track appearance this week at the Le Castellet circuit in southern France with Austrian Alexander Wurz at the wheel.
One thing is certain: The part-Goan, part-Malayali group CEO of Air Asia is not your usual boardroom CEO, and he cultivates the maverick businessman image, buying race car teams and football clubs and taking off-beat bets with his mentor and now buddy Richard Branson of Virgin.