There are several improvements over what we had before:
1. We track all the questions seen in the the student's previous
quiz attempts, so that when they start a new quiz attempt, they get
questions they have not seen before if possible.
2. When there are no more unseen questions, we start repeating, but
always taking from the questions with the fewest attempts so far.
3. A similar logic is applied with variants within one question.
There is lots of credit to go around here. Oleg Sychev's students Alex
Shkarupa, Sergei Bastrykin and Darya Beda all worked on this over
several years, helping to clarify the problem and shape the best
solution. In the end, their various attempts were rewritten into this
final patch by me.
This parallels question_attempt->minfraction, which allows the
fractional mark to go below zere.
This is needed to allow the certainty-base marking behaviours to work
better.
In the case where either a question_attempt had not steps, or a
question_usage had not question_attempts, the load_from_records methods
could get stuck in an infinite loop.
This fix ensures that does not happen, with unit tests to verify it. At
the same time, I noticed an error in the existing tests, which this
patch fixes.
1/ type/match/tests/walkthrough_test.php - tests are failing randomly, looks like some weird randomisation is going on there - see TODOs
2/ type/multianswer/tests/upgradelibnewqe_test.php contains invalid expected value - see TODO
Tim Hunt