"My first day...went really well," said the 1997 world champion in a team statement after clocking the day's third fastest time at Barcelona's Circuit de Catalunya.
"I had spent enough time in the factory for the seat fitting, so I felt immediately comfortable in the car. I did a lot of laps today and the times were good," he added.
"In addition, the car ran absolutely reliably, we had no technical problems whatsoever. So it was really a very productive first day."
Villeneuve, 33, has signed a two-year deal with the Swiss-based team. He made his race comeback with Renault in the last three grands prix of this year after being dropped by BAR in 2003.
"We have a good basis and I am confident that we can continue this work in a positive way during our next test in Jerez," said the Canadian, son of the late Ferrari great Gilles Villeneuve.
Toyota's Brazilian test driver Ricardo Zonta was fastest on the last day of testing in Barcelona this year, ahead of compatriot Antonio Pizzonia in a Williams.
The circuit will now be resurfaced, with the work due to be finished by mid-January
