Thanks, that worked. I have updated the prototype to include the extra functionality, apart from per_test_timeout which does not make sense for this prototype.
Many thanks Mark. I've added that to the "unsupported question types" repo on github, adding the line "Contributor: Mark Stern". I also took the liberty of adding 'rstrip()' method calls on both the expected and got fields when testing for correctness. I thought it was a bit odd to require newlines on all the testcases except the last one. Most (all?) the built-in question types perform rstripping in this way, and in fact also rstrip all lines as well since whitespace on the end of a line is invisible and confusing if it causes errors.
Also, I added an example question - static int sqr(int n) - since I'm trying to have at leat one example of each question type.