Robert Kubica has been back in action in a 2014-specification Williams, in a second one-day test with the team on Tuesday.
The 32-year-old Polish driver had his first outing in a FW36 last week at Silverstone. Williams did not release any details of how Kubica did at the time, other than saying the test had been "satisfactory".
This week the test took place at the Hungaroring, and the team once again declined to go into specifics. Instead, they simply confirmed that Kubica had "completed another productive day."
Kubica has already had a recent test at the circuit. He was at the wheel of this year's Renault for one day of the official Formula 1 in-season test session following the Hungarian Grand Prix.
The latest tests are part of an ongoing evaluation into whether Kubica is fit enough to return to full-time Formula 1 competition.
The 32-year-old Polish driver took part in 76 Grand Prix races between 2006 and 2010. He made his début in Hungary with the BMW Sauber team. His last appearance was in Abu Dhabi for Renault.
Prior to the start of the 2011 season, Kubica was involved in a big crash while taking part in the Ronde di Andora rally. He suffered serious injuries to his leg, shoulder and arm that prematurely curtailed his time in Formula 1.
But this year has seen renewed momentum to pick up his stalled Grand Prix career. He's reported to be a leading candidates to drive for Williams next season - if the testing goes well.
Kubica has been backed by Bernie Ecclestone. The former Formula 1 boss said that the driver could return even stronger than before, and that Williams shouldn't be afraid to select him.
Williams said that this week's test "continues our evaluations" into its 2018 driver prospects.
As well as Kubica, the team is also giving test and development driver Paul di Resta a chance to show what he can do. The Scot subbed for an unwell Massa in this year's Hungary race at the end of July.
Di Resta will be at the wheel at the Hungaroring all day tomorrow. Other candidates for the race seat next year include Sauber's Pascal Wehrlein.
Current driver Felipe Massa has also made a strong plea to be considered for another year at the Grove-based team. He says that Williams would be much worse off if it did not retain him