The deal is part of an increased association between Wehrlein and Force India, with the 20-year-old also slated to drive for the team in both of this year's in-season tests.
"I am very happy that Sahara Force India has offered me the opportunity to drive their car for two days at the official test in Barcelona and that Mercedes-Benz has supported me to make this happen," Wehrlein said.
"As a young driver, any time you can spend in the car is extremely important and you can learn a lot. I know the simulator already, but I don´t have much experience on the track.
"My first goal in Spain will be to do a great job together with the team, to learn as much as possible and to give good feedback to the engineers."
Force India will be using their 2014 car at the four-day Spanish session after experiencing delays with their new machine, the VJM08. Wehrlein, who made his Formula One test debut with Mercedes at the end of 2014, will drive the VJM07 on Thursday and Saturday, while the team's regular drivers, Sergio Perez and Nico Hulkenberg, will be behind the wheel on Friday and Sunday respectively.
"I have already driven the world champion Mercedes-Benz F1 W05 Hybrid," said Wehrlein, "and the comparison with Sahara Force India will be very exciting for me: the way the team works, how they improve the car and handle problems - all this will help me to gain experience and to reach the next level in my development.
"Everybody knows that lap times only play a secondary role when you're testing. But, of course, I want to be as competitive as possible. Sahara Force India delivered a very strong performance in the last season and I hope I will be able to make a small contribution to push the team forward and be ready for the opening race in Melbourne."
Vijay Mallya, Force India's team principal and managing director, commented: “I’m pleased to give Pascal a chance to work with us in Barcelona. He’s an exciting young talent who has already proved he has what it takes to be successful at the highest level in motorsport.
"As a reserve driver for Mercedes-Benz, he’s clearly destined for a career in Formula One and I’m sure the test will be a positive experience on both sides. Being able to call upon Pascal for testing duties is also a clear demonstration of our strong working relationship with our engine partner, Mercedes-Benz, and I thank them for their collaboration.”
Toto Wolff, head of Mercedes-Benz Motorsport, added: "This is a great opportunity for Pascal to develop his Formula One knowledge with our friends at Force India and shows the good working relationship within the Mercedes-Benz family.
"Pascal impressed us with his approach to the Abu Dhabi test last year and I am sure his feedback will be useful to Force India also. It is also a valuable opportunity for him to work with another team and gain more experience.
"This is an important year for Pascal with his primary programme in the DTM, and also these tests to build his F1 experience. We will be following his progress on both sides with great interest."