Written driving tests don’t adequately test knowledge of traffic laws

When I took my written driver’s test, I recall it being startlingly simple.  I recall in my driving class my teacher instructed my classmates and me that the answer to any question in the test that asked for a number was 100 and other arbitrary tips like that.  It was more of a memorization of answers without properly reasoning them out.  There were still many specific laws that I was ignorant of as a licensed driver that I later learned in traffic school.  Conversely, my mother who, had been driving for 30 years with no problem, had to take the California dsa practical test after we moved out here, and failed the written portion the first time.  She had all practical knowledge of traffic laws that is required of a licensed driver, and yet she was not able to reflect that knowledge in the written test.  It is clearly not an adequate representation of what a responsible licensed driver should know