The 31-year-old will therefore step up from her current role of Development Driver, which she held for three seasons.
In July this year, Wolff became the first woman to take part in a grand prix weekend for more than 20 years when she participated in P1 at the British and German GPs.
???This is another step in the right direction for me,??? said Wolff, who will also spend two test days testing the team???s new FW37 as well as performing extensive simulator work.
???I am delighted Williams are recognising my progression, hard work and that it is performance that counts. Williams is at a very exciting stage in its history and we are moving into 2015 with fantastic momentum, I???m proud to be part of the team.
???I???ll be using my position to work closely with Felipe [Massa] and Valtteri [Bottas] to make sure that the FW37 builds on the strong performance shown by the FW36.???
Williams ended this season third in this year???s Constructors??? Championship after finishing ninth in 2013.
???We are delighted to have Susie continuing with the team next season in this new role,??? Deputy Team Principal Claire Williams said. ???She continues to impress us with her strong technical knowledge, the feedback she delivers and the performance when she drives the car both on the track and in the simulator.
???She has steadily increased her time behind the wheel since she joined us in April 2012 and her appointment as Official Test Driver was a natural progression.
???We have a very strong and stable driver line-up for 2015 and this will be a key asset as we look to build on a positive 2014 season.???
The team added that they are currently evaluating a number of drivers to replace Wolff as Development Driver.