One thing that is mandatory ,yet I doubt ever gets tested .....
"speedometer is working correctly and gives an accurate reading"
obviously speedos are NEVER tested on AUDIs, Golf GTIs (or golfs pretending to be GTI, with Ebay badges,) etc 
A few years back ... maybe 10/13 
..... I presented an Astra G for test with a none working speedo/odometer.
The car passed without comment! (eventually 
)
The NT (Tester) should have noted the NON readable odometer on the certificate
what did he /she/them
put as the milage ? did he/she/them look at the ECM data
just guess
or ask YOU ,the vehicle presenter to guess
it's all down to a tester. My 4x4 ML goes for MOT to a place that can't do a rolling road brake test .... I think, by rights, he should do a deceleration test on a road test .... but has never done so. He never tests my 13 pin trailer socket either! He's never tested my reverse lights!
I still take my cars to him for test though! 
13 pin sockets are testable when fitted ,7 pin are not (there is no standard wiring configuration for 7 pin)
A decelerometer is 'probably' used when driving the vehicle into the test bay
Reverse lights would have activated getting the vehicle off the ramp , or are you still at the test station waiting for your car
I pay full fee for MOTs ,the tester (ex police) is very strict
I see that as a good thing
though I do prep my cars BEFORE presenting them for MOT ,so rarely have retests (which costs time and money)
