Always remeber the magic words 'At the time of examination' , two minutes later, your on youre own mate! I have seen a car drive up to the MOT staion, as it turned into the pit, the rear axle parted company from the bodywork. I've also had a vehicle tested, drove home in ten minutes, went to stop , and a brake pipe had burst. You can also quite legally DRIVE a failed vehicle from the test to a scarp yard. Never rely on an MOT, always make sure you are happy the vehicle is roadwrthy, then if it goes pear shaped at least you know who to blame.