** Using WeBWorK **

The default range of values is -2 to 2 for MathObjects (and -1 to 1 for the traditional checkers), and so it is possible for all the random points to be negative. The problem needs to be modified to restrict to positive values.

You can add diagnostics=>1 to the cmp() call in order to get debugging output about the points used and their values, but this only works when sufficient points actually are found.

In any case, these issues are better handled via the WeBWorK Bugzilla site rather than this question-answer site.