The Spaniard, who recently drove a Ferrari Formula 1 car at Vallelunga after winning the FIA's new European F3 crown this year, had already tested for Rapax in the Barcelona test at the end of last month.
He admitted the Italian squad was one of the options he was looking at for the 2013 season.
"I'm very happy to be driving the Rapax GP2 car again," said Juncadella.
"We are still sorting my future and we hope to do it soon, but for the time being it's good to continue with the pre-season tests and adapting to the car and the team that is one of the options we are considering for next season."
The two-day test, GP2's final fixture of 2012, kicks off tomorrow at the Spanish circuit.