I agree that there is some luck involved. You could not get to a single junction with another car, or you could have aggressive drivers honking their horns at you on every manouvere. I don't however agree with some of your examples; the possibility of a car turning into your road from a junction concealed by a bus, while you would have to be unlucky for this to happen, you would be in the wrong if you did overtake while there was a concealed junction. Some things can't be avoided, others, like poor observation can.
I failed my first test on a nervous mistake 3 minutes in, drove fine for the rest of it, was quite lucky actually, did a lot of sitting in queues. Have my second test next friday, hopefully will be just as lucky this time, and should be more confident this time, so should pass.