There's a long tail of unpredictable events in the AV industry that you end up seeing, especially since the cars in aggregate end up driving more than one could over a lifetime.

At a previous employer, we've seen anything from cars getting mooned, a SUV slowly driving past the AV, the rear window roll down, and someone poke their head out and start throwing dollar bills at the AV, a convention of people dressed up in animal costumes, the "Miami left," and so on.

So it's much less of "maybe we should test that" and more of "we don't know what we don't know, so let's gather some data." In practice, the cars have lidar so they won't crash into solid objects that aren't recognized, they just end up getting stuck in embarrassing situations like these.