I wouldn't say "super easy" but if an autonomous vehicle isn't programmed to handle:

  1: streetlight with no lights
  2: streetlight with blinking red
    2.5: streetlight with blinking yellow

Then they are 100% not qualified to be on the road. Those are basic situations and incredibly easy to replicate, simulate, and incorporate into the training data.

That is to say, they are not edge cases.

Dealing with other drivers in those settings is much harder to do but that's a different problem and you should be simulating your car in a wide variety of other driver dynamics. From everyone being very nice to everyone being hyper aggressive and the full spectrum in between.