[ethbro]

I'm tracking what you're saying now.

I'd hope they would have to demonstrate both things: (1) that a given mode can or cannot be active in a certain scenario, and (2) how the plane behaves in all tested scenarios under all modes potentially active.

Is there a reason this necessarily wouldn't be the case?

[VBprogrammer]

My guess is that it's considered so unlikely that they wouldn't be required to demonstrate the full range of behaviour. In the same way as I wouldn't expect them to demonstrate all of the edge cases of the flight envelope with a failed yaw dampener. I could well be wrong though, I haven't found any good references.