But testing also reduces ugliness: The act of making code unit testable makes it less ugly, because unit testing requires access to a portion of the code in isolation, thus making the code more modular. Modular code is less ugly (or so I claim).

That's an intriguing idea about DSLs enabling customers to see the ugliness. But why would customers look? (A parallel is non-lawyer customers looking at legal documents for beauty) Does anyone have experience with DSL's for non-developer customers? eg: SQL is a DSL for business analysts - but they develop in it, not just look at it.

This form of testing is called production. :)