Every used car changing ownership in the UAE goes through a government-approved test, at Tasjeel, Shamil or Wasel centres in Dubai, ADNOC vehicle inspection centres in Abu Dhabi, or the equivalent in the northern emirates. Sellers lean on this heavily: the car passed, therefore the car is fine. The registration test is a roadworthiness screen, and a useful one, but it checks brakes on a roller, emissions at the tailpipe, chassis integrity, lights, tyres and glass. It takes minutes.
What it does not do is open the bonnet with a diagnostic eye. It will not measure paint depth, scan the transmission module, detect a head gasket beginning to weep, notice that the timing chain is due, spot flood silt under the carpets or tell you the AC compressor is on its last summer. A car can pass its transfer test on Tuesday and need AED 8,000-15,000 of mechanical work by the end of the year, and both facts can be true at once.