In general, no testing. Unless some people are being jackasses and doing something absurd like standing on wheelchairs jousting with long sticks holding up everyone in line.
While it might be uncommon to call a wheelchair a vehicle, it fits the literal definition. I don’t understand the ‘extension of the person’ rationale, you’re still using the word ‘wheelchair’, and it’s obviously a separate object from a person. How would that rationale differ if you were talking about cars? Can I argue a car is an extension of me as long as I’m using it while I need it?
I wouldn't say I'm entirely convinced, but it's at least convincing enough that I said that a wheelchair did not violate the "vehicle" rule. I can't define "vehicle" in a way that would satisfactorily justify that decision, but I'm comfortable with that.
A bicycle actually goes on roads, follow rules and get a ticket for jumping a red light.
You can take roller skates off, get out of a wheelchair, and get off a bicycle.
Imagine you were wearing roller skates being pulled by a dog.
Imagine you were sitting in a chair, with a roller skate bound to each leg of the chair, rolling down a hill.
Imagine you were a flea in a roller skate rolling down a hill.
Imagine you were a dog in a wheelchair rolling down a hill.
Imagine you were a flea on a dog in a chair with roller skates on its legs rolling down a hill.