How does ATC control / separate Airbus Industrie test flights?
They will be in contact with ATC at all times and ATC can issue a clearance to operate within a defined area or within a specific flight level range, keeping other aircraft out of that area, e.g.


  APP: AIB97XA, cleared for turns and flight level changes in 20NM radius around ABCDE intersection, between FL70 and FL145 at your discretion.


or a bit more standard phraseology:


  APP: AIB97XA, cleared for turns and flight level changes in 20NM radius around ABCDE intersection and maintain block FL70 until FL145.


From what is visible in the French AIP, the TMA airspace of Toulouse has airspace classes D and C from different altitudes up to FL145, also in the area where your mentioned flight happened.




(Source: German NfL 1-251-14 Verfahren Sprechfunk / P. 47)