Virtual miles will probably help test known-unknowns, such as testing variations of vehicles entering an intersection but how will they test unknown-unknown com

Virtual miles will probably help test known-unknowns, such as testing variations of vehicles entering an intersection but how will they test unknown-unknown combinations such as random road debris x drivers in altered states (DUI, falling asleep) x on a steep downhill x bindspots created by nature foliage x damaged/obscured sensors?