Unit tests are a completely inadequate replacement for typing even if they actually do exist, which, as you stated, is pretty rare. I think the best compromise

Unit tests are a completely inadequate replacement for typing even if they actually do exist, which, as you stated, is pretty rare. I think the best compromise is optional typing. The language should encourage it by default, but allow some variables to be declared as dynamic/untyped. This greatly simplifies things like parsing of JSON data, which should essentially all be considered a string until there's some reason to consider it something else, but enforces consistency and safety through most of the application. Haxe does a pretty OK job with that.