Although a clutch problem led to an early shower, Kamui Kobayashi still completed 106 days on a "good" final day in Bahrain.
The popular Japanese driver is returning to the grid this season with Caterham and wrapped up his preparations in Bahrain on Sunday.
Kobayashi covered a marathon 106 laps on the day with a best time of 1:38.391.
And although his time was 5.113s down on Lewis Hamilton's P1 time, he believes Caterham have made progress on the CT05's short runs.
"106 laps is a good way for us to finish the tests, even though the clutch problem we had in the last hour meant we didn't have a chance to do any of the performance runs we'd planned for today.
"However, I'm very happy we were able to have two such good final days in Bahrain as it's showed that our reliability is good and that could be very important in Australia and for the whole season, especially when you look at how quite a few of the other teams have struggled both here and in Jerez.
"Today we had a very long program, starting in the morning with a number of short runs to work through setup changes and we've made good progress in that area.
"In the afternoon we went onto longer runs, looking at fuel and energy management strategy and tyre wear and we have a lot of data to work with on that - again, that will be critical in the races so to have had the chance to start to understand how the car behaves with different modes is very important."
Kobayashi will now head to the team's factory for a few runs in the simulator before heading to Melbourne for his F1 comeback.
"Next week I have a couple more days in the simulator at the factory and then it'll be time to go to Australia.
"I'm obviously excited about getting back to racing and with what we've achieved in testing I think it could be a very interesting start to the 2014 season."