|>>|| No. 2960
It is a known scam, but her suggestion is over-cautious.
Avoid specialists - if a garage advertises themselves as an exhaust centre and has exhausts lined up on the wall, don't be surprised if you fail on something to do with the exhaust. This is particularly nasty as IIRC you can't appeal against specific failure points, only on the overall failure.
Avoid big names like Kwik-Fit or Halfords, as they charge the maximum test fee (currently £54.85) even if the going rate locally is lower (£40 on my patch).
Otherwise, if you have a garage that you trust and they have testers, you can use them. I've been with the same garage for six years, and they've not taken me for a ride. In my area, the motor business is small enough that everyone knows everyone else, and the same names come up time and time again. If you're really stuck and don't have a relationship with any local garages, ask the local taxi drivers - anyone who rips off a cabbie will soon find the entire local fleet knows their game.