If you have a good type system you don't need to write tests like this. I test my algorithms not my function calls.

Also, > A lot of work is being done in JavaScript

Is that it? It's one of the best funded languages on Earth, what do you expect - with D for example we can do all the things you mentioned and catch errors like this, and we're basically just some guys working on the language not the combined might of the entire Internet sector.