Sauber team principal Monisha Kaltenborn says she is satisfied with her team's progress during the first test at Jerez last week.
Adrian Sutil and Esteban Gutierrez completed 163 laps across four days in the Sauber C33 at the Spanish circuit.
"We are satisfied with the first test" said Kaltenborn.
"Our car was ready just in time. The fact that the C33 functioned from the first day on track is a remarkable achievement by the team. A big compliment to everyone involved."
"We wanted to see if the mechanics and all the systems are working. The cars are very complex this year because of the new power unit, but, as a matter of fact, we have reached a good level already."
"Of course, it was also important to gather a lot of data. We have a lot of work to do, analysing the data and implementing the improvements."
Kaltenborn revealed that neither the drivers nor Sauber's engineers were happy with the brake-by-wire system, which is newly permitted under the 2014 regulations.
"Not only the drivers, also the engineers were not happy about it."
"This was a software issue in the first place. We were able to make improvements throughout the test, but there is still room for improvement. However, our engineers are convinced that they have enough time to solve those weaknesses together with our engine partner by the next test."
Sauber is expecting a fundamental update to the C33 for the second test, which will take place in Bahrain on February 19th.
"Fundamentally it’s a very extensive package. We plan to have most of the parts on the car for the first test in Bahrain. This includes new front and rear wings, side pod deflectors, as well as several other small elements on the car. A few other parts will follow for the second test in Bahrain."
Kaltenborn also warned against judging the performance of the power unit suppliers - Mercedes, Ferrari and Renault - solely on the basis of last week's test.
"The only thing you can place in an order is the number of laps the teams did with the respective engines. Here the order is clear: Mercedes, Ferrari, Renault."
"But to compare the performance is impossible at the moment, also because some might still be playing their cards close to their chests. I am sure there will be movement right up to the first race in Melbourne in that regard. At the moment this is just a snapshot."