Williams F1 technical director Sam Michael said he was pleased with a productive test for the Toyota-powered squad after wrapping up a four-day session at Jerez.

Test driver Nico Hulkenberg and race drivers Nico Rosberg and Kazuki Nakajima all spent time at the wheel of the new FW31 during the test in Spain as the team set about improving its package ahead of the season-opening Australian Grand Prix, and Michael said he was pleased with how the test had progressed.

"This week we had all three drivers working on aerodynamic and mechanical set-up optimisation while also evaluating tyres for Bridgestone," he said. "The main target at the moment is to improve the balance on slick tyres, something we are all learning about as quickly as possible. We completed all of the systems, reliability and aero checks that we set out to at the beginning of the week.

"We finished off the test with some pitstop practice work with the race team so they could get used to all of the new equipment, and to give the drivers an opportunity to get used to pitting on slicks. It's been a productive week and we are looking forward to the next test back here in Jerez in the first week of March."

Both Rosberg and Nakajima were also pleased with the way the test had progressed, with Nakajima stating it had been a 'positive start' and Rosberg giving the new car a firm thumbs up.