The Frenchman joins Finn Juho Hanninen, who was the first driver announced by Hyundai last week.
The German-based team intends to run numerous other drivers this season as it ramps up development of the i20 WRC ahead of its World Rally Championship debut in six months.
Bouffier, who will test the i20 for the first time today, said: "I'm pleased to be joining Hyundai Motorsport's test programme and to be part of the team for this year.
"It's true that there is a lot of work to do, but the team is in place and the facilities are impressive, so we have good foundations to build upon.
"This is an exciting programme and I'm sure the summer time will be very busy and hopefully just as productive."
Team principal Michel Nandan added: "I'm happy to have Bryan on board. He adopts a very professional driving style and can give detailed technical feedback as well as being a very consistent driver, which are all very important attributes for a test driver.
"Together with Juho's experience of WRC events and his speed on all terrains, I am sure we have a strong and well-rounded line-up for our testing programme."