Whether speeding by 1 mph on your driver's test automatically results in failure depends on the specific rules and regulations of the jurisdiction where you are taking the test. In many places, exceeding the posted speed limit, even by a small margin, is considered a violation and could lead to failure of the driving test.
During a driver's test, the examiner is assessing your ability to follow traffic laws, demonstrate safe driving skills, and adhere to the rules of the road. Speeding, even by a small amount, is typically considered a serious infraction as it can pose a risk to yourself and others on the road.
However, some jurisdictions may allow for minor mistakes or slight deviations from the speed limit as long as they do not present significant safety risks. It is essential to consult the specific guidelines and regulations set forth by the relevant licensing authority in your area to understand the precise requirements for passing a driver's test.