RFC: Change rules for adding/changing test cases

[DJ Delorie]

> We find it very useful to have substantial chunks of real application code
> in different styles in our test suite. Not to test anything very specific, 
> but just to test general robustness.

Hmmm...  I don't know how to integrate that into my proposal.  Still,
when appropriate, comments in test cases about how previously found
bugs were fixed would be helpful, especially backend/frontend bugs (vs
bugs in common code).