For example some master plumbers exams require the candidate to know how to size a suds pressure zone.
A lot of tests ask math questions like they will ask velocity from GPM flow at a certain pressure.
Some tests also give you a constant like 1.4142 and ask where would a plumber use this (45 Degree offset center to center measurement).
A lot of code questions also are based on local areas (frost level for one and actual specific gravity of the gas in your area plus the BTU rating and delevoped lenh of piping when supplying several appliances and sizing accordlingly)
The sizing of the fresh air inlet and its relation to the building house trap if applicable and the minimum size.
A favorite question also that appears is where would hoarfrost occur, vent water supply, etc.?
Some questions are based on common sense like “Why is a man hole cover round”?
Fixture units and developed length also used for sizing vent piping is not required on ever code as some never take DL into consideration.
As a master plumber there is one test (in NYC anyway) that covers everything from hospitals to high rise buildings to one family homes and the code questions can be based on any of the following including sizing the roof drainage and using interpolation of storm to sanitary lines to find a combination sewer size.
Acid waste questions as to materials and venting are also part of the code questions that must be answered PLUS the practical tests and business questions.
The best thing to do is ask your locality for their requirements.