I work at Pivotal, arguably one of the most test-obsessed companies in the world. Tests and types are not direct substitutes. My view these days is that types

I work at Pivotal, arguably one of the most test-obsessed companies in the world. Tests and types are not direct substitutes. My view these days is that types become more valuable as a codebase grows. I have worked on Ruby on Rails codebases where, quite frankly, I found myself wishing it out loud was Java on Spring Boot. (Many of my peers in Labs are flatly enthusiastic about Kotlin on Spring Boot, FWIW) In the same genus as the "just use tests" argument is "business logic only belongs in the app, not the database". Yeah, well, it turns out that no amount of testing is a substitute for constraints and transactions.