Interesting how OO-focused this is. I work at Google today, in relatively old C++ and JS (now converted to TS) codebases, and we have no particular emphasis on forcing every function to be a method of a class. I don't think this has especially harmed testability.
What part of OO was about testability? Single responsibility? Liskov substitution? Interfaces to test instead of implementations? Just chunking things into bite-sized pieces?
