Support Testing With / Without Debug Constraints

[DavePearce]

The goal here is to test both with debug enabled and without. This is challenging because we need the tests to function the same regardless as to whether debug is enabled. Of course, that's what it is intended for ... but it still needs some thought.

NOTE: a good way of doing this would actually be to allow the tests to specify when they can and cannot be run with debug enabled. That would actually make testing easier.