If DHH's main concern was practicality he wouldn't advocate UI & DB tests which are flaky, unreliable and expensive to maintain for any non-trivial application.

Code and system architecture absolutely should be bent to the needs of testing. Pretty and "clever" code is useless unless it does what it's supposed to do.

UI & DB tests absolutely have their place - I'm not disputing that at all, and I completely and whole-heartedly advocate their use - but they need to be used in conjunction with very fast, very reliable (and thus very useful) unit/integration tests that have been TDD'd.