I know TDD has gotten out of fashion, where people seem to acknowledge today that the right balance of tests is better, more practical, then a test first and test everything approach.

Formal verification hasn't really caught on yet. The extra effort needed to formally prove even a trivial program seems to be too high for the value it gives to most stakeholders.

I'm really hopeful for simpler methods of formalized proofs, or even automated testing. I think today, the practical cost is maybe still too high for people to care.