Sporting a plain white helmet and overalls, the 26-year-old Spaniard completed several laps in an unbranded MP4-21 at the 4.42-kilometer (2.748-mile) circuit.
"I have a strong relationship with the Renault F1 Team and I would like to thank Flavio (Briatore) and Renault, who have agreed to my request to test one day with my new team," Alonso said.
McLaren had previously asked Renault to release the defending champion from his contract, which runs to Dec. 31, reports AP.
"Fernando asked me to test one day with his new team to acclimatize himself to the car," Briatore said. "We enjoy a very good relationship and considering his work and his fabulous achievements these past two years with the double world titles in 2005 and 2006, we decided to give him this opportunity"
Alonso is scheduled to test with McLaren at the Cheste circuit in Valencia from Jan. 14-16.