Spanish Grand Prix winner Nico Rosberg set the pace on the opening day of the first in-season at the Circuit de Barcelona-Catalunya.
Rosberg posted a 1:24.374 in the morning to jump to the top of the timesheets and his time remained unbeaten for the remainder of the day.
Marcus Ericsson was second quickest for Sauber, ahead of Raffaele Marciello in the Ferrari.
Daniil Kvyat ended the day fourth, despite spending most of the morning confined to the Red Bull garage, with Pastor Maldonado fifth for Lotus.
Nick Yelloly made his testing debut for Force India a day ahead of schedule with Pascal Wehrlein suffering from a fever, with the GP2 racer sixth fastest on his first run in the VJM08.
Pierre Gasly got his first taste of a Formula 1 car with Toro Rosso, setting the seventh quickest time of the day, and will drive for the senior Red Bull squad on Wednesday.
Felipe Massa went eight for Williams, ahead of long-time McLaren tester Oliver Turvey, who round out the order in ninth.
Testing continues at the Circuit de Barcelona-Catalunya on Wednesday.
Image courtesy of Daimler