I agree that the test would be best suited to in the air
That'd make sense...
For the record - in Oz we don't do an R/T 'test' as such, we just get issued a 'flight radio operator's licence' before GFPT... so your instructor makes an 'assessment' while you do your initial training. No 'examiner' needed, much easier all round!
The 'test' as described by MyData seems a bit contrived to me, doesn't bear much resemblance to a real situation - so you'd be studying to pass the test rather than to know your stuff. Doesn't make sense to me...