Typical Rails codebases already enjoy a reasonable layer of 'typing' via ActiveRecord coercions, validations, and possibly some system that declares/documents t

Typical Rails codebases already enjoy a reasonable layer of 'typing' via ActiveRecord coercions, validations, and possibly some system that declares/documents the types/structure of your REST API. Also, I advocate keyword arguments (especially 'required' ones), which tend to kill 80% of the use case of typing for dynlangs ("what's the type of argument x?") A meaningful test suite would hammer the last nail in the coffin.