[nickjj]

Having a statically typed language doesn't mean you don't write tests.

Sure, there's a subset of tests you can avoid writing but you're still going to be writing a ton of tests with both language types. I also think this point gets blown out of proportion. For example I don't write a ton of boilerplate "what if I pass X type to Y variable" types of tests in Rails because I trust the database and Rails' validations. For example if I have a datetime field in a DB which is automatically defined as a datetime in Rails I'm not going to write a separate test for what happens if I pass in a string, integer, boolean, list, hash and so on. I'd write a test around making sure the date is within a specific range if I hooked up a validation rule to it to limit the range, but I'd write the same test with a statically typed language too.

Also, Stripe has a good write up[0] on how they use Sorbet to add type checking for Ruby and how they applied it to a multi-million line code base without disrupting developers too much. Basically a small team did most of the work, including writing the tool and migrating the code base. I haven't used it personally but it exists and can be used successfully at scale.

[0]: https://stripe.com/blog/sorbet-stripes-type-checker-for-ruby