The design integrity of your system is far more important than being able to test it any particular layer. Stop obsessing about unit tests, embrace backfilling of tests when you're happy with the design, and strive for overall system clarity as your principle pursuit.
I think it's hilarious that TDD has gone too far for DHH. And I like his thoughts around the matter - test what's important, at the important levels. Don't add dozens of gems and layers of indirection and library magic just for testing.