Dozens of Polish media and thousands of his fans cheered the 32-year-old as he got to grips with Renault's 2017 car in the recent Hungary test, notwithstanding his permanent injuries sustained in a crash six years ago.
Ricardo Penteado, a leading Renault engineer, said that any doubts about Kubica's ability to drive a modern F1 car evaporated at the test.
"You can forget that question - he has no problem to drive the hybrid cars," Penteado told Brazil's Globo.
Kubica's best lap in Hungary was competitive, but Penteado said that the 2008 Canadian Grand Prix winner could also have been quicker.
"The most important thing is that Kubica did not have fuel for just one lap," he said.
"The other thing that stands out is the number of laps he did - the equivalent of two races. It was 40 degrees and Robert did not get out of the car complaining of exhaustion."
Finally, Penteado said that Kubica was able to drive the Renault with only minimal changes to the layout of the steering wheel.
"He had no difficulty," he said. "We asked for a lot of changes from him via the steering wheel, and he did everything within the normal time."
Kubica drove for BMW Sauber and Renault prior to his 2011 crash.