McLaren's Alexander Wurz topped the time sheets at Valencia, for the second day in succession.
Having out-paced the nearest opposition by 1.6s on Thursday, on the final day of testing the gap was down to 0.782s.
It was a trouble-free day for the Woking team, which now heads to Barcelona, where it will debut its 2005 contender, the MP4-20.
The Spaniard pursued his adaptation to the 2005 regulations while his French teammate concentrated on suspension development.
Fernando's programme focused on adapting to the new regulations and their impact on race management. He therefore tested tyres and set-up solutions on long runs in order to understand more about how to get the most from the car in this configuration. On the other side of the garage, Franck worked on suspension development, completing a programme which will be transposed to the R25.
"We concluded the week with a good day," said chief test engineer Christian Silk, "and Fernando completed plenty of laps while settling in to the set-up and tyre characteristics of the new regulations. The team is working well after the winter break, and we are all excited about giving the R25 its first run next Tuesday."
The R25 will make its track debut on Tuesday 25 January, with Alonso at the wheel for two days. Giancarlo Fisichella will take over from his team-mate in the new car on Thursday 27 and Friday 28 January.
Felipe Massa was on duty for Sauber, the Brazilian completing 110 laps. Although 1.3s off the pace of the McLaren, the C24 was the quicker of the 2005 car in action, out-pacing Davidson's BAR by 0.284s.
It was a difficult day for the Englishman, who like Jenson Button on Thursday, suffered an engine failure. This is bad news for Honda ahead of a season when powerplants must last for two race weekends.
Davidson finished the day fifth quickest, 1.595ss off the pace, ahead of fellow BAR tester Enrique Bernoldi.