Self testing
Can't speak as an expert on all A320 systems (worked on software for the 320 FQIS in the 80s) but its likely that all software managed systems in any modern aircraft will have built in self test (BIST/BIT/BITE) routines that run at start-up, at shut-down and perform monitoring and test processes during flight.
This is normally passive in nature (checking sensor values and states are in range) but I'm sure many systems will perform more "active" tests to ensure operational safety before engaging key systems.
Engines and gearboxes etc also have Heath Usage Monitoring Systems (HUMS) built into the software. This is BIT (though normally passive) by another name.
Self tests are all over the place and help systems spot potential issues and problems BEFORE they become significant - often allowing maintenance and replacement of parts before anything fails to a level that would cause a cockpit warning.
The pilot would not be aware of any of this.