Two weeks would seem about right for most aircraft , something simple like a Cub a little less.
At the moment spare parts ordered from the USA are in some cases taking much longer to get across the atlantic as they are getting "bumped off " flights in favor of high priority military cargo , this situation should ease over the next few weeks.
Also remember that the weather has to be OK for the C of A airtest , it wont take much turbulance to put the rate of climb below the -80 ft/min that the CAA will except so getting the right day for the airtest will save you the time and expence of doing it twice.