Fernando Alonso believes McLaren has the potential to have the best chassis by the time the European season begins in May, having sampled the MP4-31 for the first time.
McLaren slumped to ninth in the 2015 standings amid reliability and performance issues but Alonso was able to rack up over 100 laps at the Circuit de Barcelona-Catalunya.
Alonso ended the day in ninth position, but spent substantial time evaluting "not very exciting" aspects such as "aerodynamic studies, reliability, brake temperature, water temperature."
While expecting Mercedes, which logged 172 laps courtesy of Nico Rosberg on Tuesday, to continue its superiority at the front of the grid, Alonso reckons McLaren can have the best chassis within a few months.
"I think Mercedes' domination did not finish, they are very strong, they are doing some interesting day now in testing with that amount of laps, it means you have very clear things," Alonso told assembled media, including F1Zone.net.
"When they put the potential they are stronger than ever, even more than the last two years, to win is not an easy task but I am proud of the team in the last two months.
"I think the target to have the best chassis is achievable, something possible, by the European races and motivation is very high.
"There is not a magic solution or crystal ball but I would like to be competitive and fight for something important."
One of McLaren-Honda's biggest weaknesses in 2015 was energy deployment and Alonso was encouraged by the improvements on Tuesday.
"Definitely yes but this is let’s say an answer that I had no doubts," he said when asked if he noted improvements.
"We could not have any doubts, the starting point of the power deficit we had compared to top teams was just too high, we did improve all areas of the car.
"I think on the aerodynamic side there are some parts which are quite innovate or new, maybe the others they had these ideas in the past but for us they are new and we need a little bit of time to mature the project, the package, and in the power unit the same thing.
"Last year was a lot of learning, a lot of pain, but we learned many things and now with a new design and philosophy and power units we still need a little bit of time for understanding and to exploit the potential."