How to properly assess a student's knowledge of a subject
I have found a couple of resources regarding the question of credibility of examinations.

The University of Michigan advocates that examinations should be:


Valid, (providing useful information about the concepts they were
designed to test)
Reliable (allowing consistent measurement and discriminating between
different levels of performance)
Recognizable  (instruction has prepared students for the assessment)
Realistic (concerning time and effort required to complete the
assignment)  (Svinicki, 1999)


For others' reference:

https://www.cmu.edu/teaching/assessment/assesslearning/creatingexams.html

http://www.crlt.umich.edu/P8_0 &lt;- referenced UofM material above can be found here.

P.S. - The UofM website has further references, including the '(Svinicki, 1999)' that is listed above.