There is no AFM requirement, neither an FCOM procedure, to perform such test.
Navigating the Airbus document set is tricky waters at times. Your drive to double check before believing what you see is very prudent. Whenever I did it served me well, and v.v.
(On a previous type wing AI would operate continuously on GND if selected on, and we had a caution in the manuals no to use it after application of fluid, similar to what’s been said above.)
. I do not think there is any Airbus OEM guidance, or they would bother issuing one, as this is a complete non-issue
. should the company insist on verifying the correct operation before use (*), why not be smart about it and do it before spraying? The places you’d get de-iced before engine start are extremely few.
. maybe the esteemed TRE was trying to pass on knowledge, and ventured too far beyond the bookshelf? That’s an easy slip when the trained crew comes thoroughly prepared and they already understand well what is in the manuals.
* = such steam gauge, late 60’s philosophy had been designed out of this aircraft. Think STBY compass movement check.