These files, contributed by Boyd Duffe, are an example of writing unit tests 
for PG modules so that we can determine (a) that they work, and (b) that they continue
to work when some seemingly innocuous change elsewhere in the system causes troubles
in this module.  

Of course this is not supposed to happen when modular programming practices are followed
but it happens anyway. :-)

We need more "unit tests" like this.  (The unit does not refer to Unit.pm but to testing
a small piece or unit of the WeBWorK/PG code.)  I would also like to wire these
in so that administrators can perform these tests from the admin page on the web
to reassure themselves that the new version of PG they are using is functioning correctly.