yes, but that's only for objects that you have spec(ified). It really would be a lot of work to do for every variable, and you'd quickly hit the point of diminishing returns.

Another thing to consider is how many of your bugs are because of an ill specified object, or because i held null instead of integer.

I'd be surprised if the standard library wasn't spec'd up front, so you'll get that for free at least. Seeing as spec also generates tests and whatnot, it seems like a worthwhile investment for your own functions, if you were intending to write tests anyway.

Also, I think the idea is to write specs for stuff that happens on the edges of the app, such as data received on the wire. If you have that covered, it probably would catch most problems you might encounter, such as receiving a null in a place where you expected a positive integer or such. Since it also destructures the data for you, specs for stuff received on the wire would save you the time you'd otherwise spend taking it apart manually, while simultaneously making sure it's not malformed.

Although I'm not that thoroughly read on spec, so I'm not sure I'm taking everything into consideration.