Swiss Buemi, and Portuguese da Costa, will be the joint test and reserve drivers.
Dec.6 (GMM) Red Bull on Friday confirmed reports it has signed up two test drivers for the 2014 season.
We reported last Tuesday that incumbent Sebastien Buemi, and newcomer Antonio Felix da Costa, will be manning the world champion team's simulator amid frenzied development under the radical new regulations.
Red Bull confirmed in a media statement on Friday that 25-year-old Swiss Buemi, and Portuguese da Costa, 22, will be the joint test and reserve drivers.
"Next year sees the biggest change to the regulations for some time and the return of multiple in-season tests," said team boss Christian Horner.
"To therefore be able to call on two such capable drivers is of huge benefit to the team."