The flight test program for the Mirage was conducted at Avalon because that is where the final assembly of the aircraft was completed.
ARDU was based at Laverton but their flight test program was separate from the initial acceptance tests, etc for the newly built Mirages.
The pilot who landed the Mirage at Laverton prior to the airshow was not a test pilot when this occurred with squadron authorisation.
I am happy to be proved wrong, but I am pretty sure that this did happen.