Mercedes' reserve driver Pascal Wehrlein had been due to drive for the team on day one, with Nick Yelloly getting his first taste of Formula One machinery on the second day. Wehrlein, however, had to withdraw due to illness, prompting Force India to shuffle Yelloly to day one and turn to Ocon for the final day.
The 18-year-old Frenchman has previous F1 test experience - he drove for Lotus at the end of 2014 in Abu Dhabi, when he was also the team's development driver.
Now affiliated with Mercedes - the German manufacturer supports his career and has an option to make him a "fully-fledged Mercedes-Benz driver" in the future - Ocon has a strong pedigree in single-seaters, having beaten Max Verstappen to last year's European F3 crown and won on his GP3 debut at the weekend in Barcelona.
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.
Full testing driver line-ups:
|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|