That is really a hard question to answer. It can take anything from 1 week to 3 months. It all depends on many factors including:
How many vehicles are available for use
How many cycles per vehicle
Authority Testing (TUV / CSEI)
Mandated fault free cycle testing (CSEI is 80 hours no fault)
How many brake runs as this helps distinguish how many zones
If its a small coaster, you could be done in 2 weeks. If its a large dark ride it could take 4 months.
So yeah - not an easy answer.