Hamilton bounced back from an accident on Wednesday to complete 145 laps on the final day of running.
"Today we managed the kind of mileage that the car is capable of and I think we have a good platform to start working from," he said.
"Now we need to understand the F1 W04 even more: personally, I am learning something with every lap I do and every change I make to the set-up."
"Overall, I think we are probably at the level we would have hoped to be. The team has done a great job to add downforce to the car over the winter and they now need Nico [Rosberg] and me to tell them where we can improve and the direction we need to go. Everybody has been incredibly supportive and I am really building a good bond with the team; they feel energised, ready to go and everybody is working flat out to move us forward."
Team principal Ross Brawn also believes Mercedes has taken a step forwards.
"After a difficult first half of the test, the last two days have really been as good as we could have hoped for," he said.
"Nico is probably best placed to compare between last year's car and the new F1 W04 and he seems pretty enthusiastic, but it is hard to have any reliable feeling of where we stand relative to the competition."
Brawn also praised Hamilton's contribution to the team.
"Lewis had a very constructive day today as he settled in to the car; he has been very straightforward in telling us what he thinks, is interested in everything about the car and has a very good eye for detail. Overall, the step we have to make from where we were at the end of last year is substantial and it is also, of course, a moving target. But looking at the team as a whole, I can see very encouraging signs of progress."