In this way, TDD purism belongs to the world of dynamic typing; being a TDD purist in Rust is a mistake, but being a type-driven designer in Ruby is also a mistake.
https://lexi-lambda.github.io/blog/2019/11/05/parse-don-t-validate/
https://blog.ploeh.dk/2015/08/10/type-driven-development/
https://duesee.dev/p/type-driven-development/