Robert Kubica concluded his first day of running at Yas Marina with Williams' FW40 with 100 laps and a fairly irrelevant eighth fastest time.
The Pole focused on short performance runs while sampling a range of Pirelli tyres before undertaking longer stints, recording a best lap of 1m41.296.
The time, which was about 3.5s off Kimi Raikkonnen's fastest lap, was perceived as irrelevant given the specific nature of tyre testing, when drivers test a diversity of rubber and settings.
Lance Stroll took over for the afternoon but Kubica will be back behind the wheel on Wednesday afternoon following a test in the morning by Sergey Sirotkin.
Kubica's test was looked over by Williams' top engineering brass made up of Paddy Lower and Rob Smedley, but part-time manager Nico Rosberg was also present to oversee the run.
The test was free of any drama and Williams was reportedly pleased with its driver's performance and feedback.