yes, a lit abs light will fail the MOT test. It could be a failed abs pump or wheel sensor, it needs to have its fault code read to see which component is causing the problem. My Xedos 6 does light its ABS light but I can manage to get the light out again by turning off the engine, waiting 5 seconds and then it will go out. My Xedos 6 is going to my local council test centre in 2 weeks time and I have checked that as long as I can make the ABS light go out it will pass the MOT, ( I work for the council and know most of the mot/taxi testers ).
Rob H