Revert "Revert "Backfilling tests""

This reverts commit 131c5286f6cff385a76f40c60b4c531027431fe8.

This was not a Ruby 2.0 incompatibility.  Instead I was not accounting
for the fact that these tests were mutating classes which were not
reloaded between tests, and the failure only occurred on certain
orderings.  So now each test operates on a different class.