The acceptance test we carry out at my company is derived from the one provided by the manufacturer. Additional test requirements are then mandated by the NAA.
Without going too much into detail here are some of the items included in the test schedule.
-Packs off at altitude to check cabin rate and cabin alt warnings (horn, mask drop, etc.).
-Fuel pumps off at max gravity feed altitude.
-Engine shutdown and restart.
-Engine acceleration checks.
-Stall warning.
-Fuel jettison.
-Alternate gear extension.
-Overspeed warning at all configurations.
-GPWS test.
-Handling checks on single hydraulic system.
-APU start and operation at max altitudes.
Basically it is about checking that system operate normally at the limits of the normal operating envelope.
How long it takes depends to some extend on weather and traffic conditions.
3 hours seems to be the norm.
This is for a widebody twin.