Following a tough campaign last year when Alonso just missed out on a second Formula One world title to Sebastian Vettel, the Spaniard skipped the first test in Jerez a fortnight ago.
Rather than getting acquainted with the new car, Alonso chose to focus on his training, allowing team-mate Felipe Massa and Pedro de la Rosa to put the F138 through its paces.
Now Alonso is set to take up the reins today at the Circuit de Catalunya in Barcelona.
A Ferrari spokesman said: "Fernando has had a physical preparation worthy of the best Olympic athlete.
"Now he is ready to slip into the F138 and benefit from all the work of Felipe and Pedro in Andalusia. This week it will be Massa to sit out for the first three days, with the handover scheduled on Friday."