The test at our school lasts 1 hour.
But, as that includes all of the lower belts, when testing for yellow, we were able to sit down after the first 15 minutes or so, while the higher belts continued their tests.
At our school ... yellow belt testing consists of ...
13 techniques
Short Form 1 (sometimes, the Head Instructor works both sides)
Blocking Set 1
The instructor may ask a few questions. The students may have to recite some pledges.
In the week leading up to the test, there are some physical requirements that must be met ... sit-ups, push-ups, heavy bag punches, kicks, and sparring rounds. At the Yellow belt level, these requirements may take 30 to 45 minutes total time to complete.
The test is private. A promotion ceremony is held later, usually the next day, where all friends and family are invited.