Toro Rosso says Luiz Razia's proficiency on his first day with the team led to a productive first day of testing in Abu Dhabi.
The Brazilian has previous F1 experience, having tested several times for Caterham and also earlier this year for Force India.
Razia, runner-up in this year's GP2 championship, ended the day sixth fastest, having helped the team evaluate its aero and brake systems across the day.
"This was Luiz's first day working with us and he acquitted himself well, quickly getting into a rhythm and running at a good pace," chief engineer Laurent Mekies said.
"This meant we got plenty done, on a day when the track conditions were nice and stable throughout the session.
"In the morning we did some aero testing, switching to brake system evaluation in the afternoon."
Razia said his previous knowledge of the Yas Marina circuit had eased his first day with the squad.
"I enjoyed my first experience working with Toro Rosso today, on a track I know well, having driven here in 2010 and '11," he explained.
"In the morning, the team had various test items it wanted to work through and in the afternoon, we looked a bit more at establishing a base line on the car.
"Overall, it was a good day as the car ran trouble free and I was able to do a lot of laps."
Razia will hand over control to Johnny Cecotto Jr tomorrow, before resuming Toro Rosso testing duties for the third and final day.