Car goes in for MoT, fails because fog light is knackered. Get it fixed, take it back a few days later.
Do they have to do the full MoT test or can they just check the bit if failed on (fog light)?

Ta :)

as far as im aware they just retest the failed part.

Yeah they do,just retest the failed bit
:)

If the vehicle is taken away for repair, then they are within their rights to do a full retest and charge for it!
dave

The above is true, but most don't bother to be that much of an arse. The one thing above the fog lamp, that they will have to retest are the emissions.

They will test only the fog light as long as you take the fail certificate with you. No fail certificate and it's a full re-test (I fell foul of this many years ago. Same garage, same tester. He remembered me and knew what the car had failed on, but inisted on the fail certificate or a retest).

Doug

Had experience of this recently. They will retest the failed area and do the emissions test again. They have the right to charge a retest fee up to £40.75 maximum if you take the car away for repair and return for retest.