Comment by stevepotter

Agree on the importance of testing. Among the production-grade codebases I've worked on, I've found that the dynamically-typed ones have more comprehensive testing. It's just so easy to think that a successful compile means your code will work. I've also found that it's harder to set up great test systems for static languages because you often have to modify your logic just to make it testable (looking at you, IoC). A delightful test system is one that engineers will use during development because it saves time, not an afterthought. For whatever reason, I haven't ever found something that provides this type of experience out of the box. In one organization, we spent months building a rig and achieved true TDD. The result was fewer production issues, faster development, and of course, better test coverage numbers. We eventually switched from javascript to typescript, but it didn't compare to the difference that test system made.