Wat. I have no idea what you're going on about. The customer doesn't care about the particulars of your unit or integration tests, instead they care about whet

Wat. I have no idea what you're going on about. The customer doesn't care about the particulars of your unit or integration tests, instead they care about whether your software works properly. A modern, powerful static type system is one tool that helps a developer achieve that goal of properly working software, and the developer absolutely should care about whether that function argument is an integer or a string.