Mercedes team principal Ross Brawn has claimed that he is pleased with the progress the car is making, but admitted that there is still a lot to do.
Both Nico Rosberg and Lewis Hamilton tested the car during the past week in Barcelona, finishing in times within a second of leader Sergio Perez in his McLaren.
Brawn though, has insisted that the car is on target.
"Overall, we've had a good week in Barcelona and achieved the program that we set ourselves for this second test," Brawn said.
"Nico and Lewis are becoming more familiar with the car and it's behaviour as each day progresses, and Lewis is settling into the team very well.
"We now have just four days of testing left until the first race in Australia, and a lot of work will be done before we return to Barcelona next week."
The first race of the 2013 season is in Melbourne during the weekend of March 15-17.
