If a vehicle experiences an unforeseen mechanical breakdown during the practical test (e.g. alternator failure), how does the GDT handle the test?

1. The candidate is automatically failed, because stalling and failure to start are disqualifying however they are caused
2. The candidate must complete the test on foot along the designated route
3. The candidate is barred from testing for six months
4. A genuine mechanical fault falls outside the disqualifying criteria, so the fault itself does not count against the candidate