In my case the Engine Test was conducted right after the Theory Test.

I was shown a black and white photograph of the engine bay (under the hood) and the examiner pointed to certain parts and asked me the identify them. The parts asked were - brake fluid reservoir, power steering fluid reservoir, radiator, radiator coolant reservoir, windshield wiper reservoir, engine oil reservoir and battery.

Make sure you can identify the radiator, the radiator coolant reservoir and the battery. Because these are the parts he was asking in the end and seemed to be basing his decision on.

p.s. In my friend's case he was shown a colour photograph and asked to identify similar parts.

All the best.
Stay cool and you will pass.