Very curious to hear about the specific cases where types make tests unnecessary.
I spend my working life swapping between Ruby and typescript projects and the typescript project is utter garbage with poor test coverage that needs a day of human QA for every build whereas the Ruby project is well tested such that we know that CI passing means it’s good to be released.
Types don't make testing in general unnecessary, but it removes a class of error handling that runtime type checking handles for you. You can really trust the types when using Sorbet.
(I also work in a 40m+ loc non-rails ruby codebase that is almost entirely typed with Sorbet.)
Haha “tell me you work at Stripe without telling me you work at Stripe”