The project was first made public in a presentation made by Undersecreteriat for Defence Industries, (SSM) during the 7th Naval Systems Seminar in 2017. SSM simply told that they have signed a contract for a Test and Evaluation Ship.
More information was released in a presentation made by the engineering company STM during the same event. According to STM, they are the main contractor of a project, where one Test and Evaluation Ship (TaES) will be constructed by Istanbul Denizcilik Shipyard. The ship will have hull form of Ada class corvettes. Aselsan, as a subcontractor is responsible for the manufacturing of the mission systems to be used on board.
STM also shared the above photo. The ship showed there has a striking resemblance to Ada class corvettes. Two most obvious differences between this ship and the Ada class corvettes are this ship doesn’t have a gun in A position and any other weapons. The space between the mast and the funnel, where 8 Harpoon missiles are installed in Ada class ships doesn’t exist in the TaES. The aft of the superstructure is also slightly different. The superstructure aft of the funnel is larger since the TaES doesn’t have the STAMP remote-controlled gun system and anti-torpedo countermeasures system, the deck on which these systems are installed is added to the hull.
According to news reports, the TaEs will have an all diesel main propulsion whereas the Ada class ships have a combined gas turbine and diesel engines as main propulsion. The top speed of the TaES will be lower than Ada class corvettes.
Since TaES shares the same hull and superstructure of the Ada class corvettes, I believe the physical measurements of the TaES will be same or very similar of Ada class ships.