Frenchman Gasly, a Red Bull junior, comes into the test on a high after scoring his maiden GP2 podium at the Spanish venue on the weekend. The 19-year-old will drive for Toro Rosso on day one, before switching to parent squad Red Bull for the second and final day.
British driver Yelloly, a race winner in GP3 and Formula Renault 3.5, will meanwhile get behind the wheel of Force India's VJM08 on day one, a day earlier than expected after Mercedes' reserve driver Pascal Wehrlein, who was due in the car, was taken sick on Tuesday morning. Wehrlein is also due to test for Mercedes on day two, when Alex Lynn and Esteban Gutierrez will also enjoy their first runs for Williams and Ferrari respectively.
Lynn joined Williams as their development driver ahead of the 2015 season, after securing the GP3 crown last year. The 24-year-old Briton, who has tested previously for Lotus at the end of 2014, comes into the test on the back of his breakthrough GP2 victory on Sunday.
Gutierrez was signed by Ferrari as their reserve driver for 2015 after losing his F1 race seat - which he had held for two years - at Sauber. The Mexican will take over from the Scuderia's Italian protege Raffaele Marciello, who will then transfer to Sauber for day two.
Day two will also see Lotus third driver Jolyon Palmer at the wheel of the team's E23 Hybrid, and McLaren test driver Oliver Turvey - currently competing in Japanese Super GT - taking control of the MP4-30.
The 28-year-old will take over from Jenson Button, who will be hoping to get to the bottom of handling issues that he said made for a "pretty scary" Grand Prix on Sunday.
Button is one of just seven race drivers in action, with none of the nine teams involved - Marussias will skip the test - opting to use their full 2015 race pairings.
Formula1.com and our official Twitter channel, @F1, will bring you all the latest news, images and reaction throughout the two-day test in Barcelona.
The provisional driver line-ups in full:
|Mercedes||Nico Rosberg||Pascal Wehrlein|
|Ferrari||Raffaele Marciello||Esteban Gutierrez|
|Williams||Felipe Massa||Alex Lynn|
|Red Bull||Daniil Kvyat||Pierre Gasly|
|Sauber||Marcus Ericsson||Raffaele Marciello|
|Lotus||Pastor Maldonado||Jolyon Palmer|
|Toro Rosso||Pierre Gasly||Carlos Sainz|
|Force India||Nick Yelloly||Esteban Ocon|
|McLaren||Oliver Turvey||Jenson Button|