Just had mine done... it failed! My fault though on both counts. Firstly, I've fitted a R&G Tail Tidy, and I'd forgotten to attach the little sticky reflector, also, I'd been running blue side-light bulbs, and didn't put the stock ones back in for the test, D'oh!!
On the plus side, it took me exactly 10 minutes to sort it when I got home, and I get a free re-test within 14 days, as they were only minors.