[pavelkaroukin]

For projects I am doing on my own (albeit, these are quite simple, just fun ones) I am doing TDD approach.

It is really natural to me, because part of developing idea is a research. It often includes doing some test of how particular library works, what format of data expected, etc. I always was finding myself doing small isolated programs/scripts to test specific question I have about it. And now it was so natural to start using TDD approach.

As other commenters noted, due migration of much logic to JS (client) side, testing it together with server app might be a challenge. For my particular case I "solved" it by using V8 library. I am developing with Perl language and there is great libraries available on cpan. V8 and pure Perl ones. I am using V8 for performance reasons (doing encryption), but before I used pure Perl JS library and it worked perfectly too.

So if your language of choose have libraries to hook into one of JS libraries, I would highly recommend to try to include JS tests into application tests kit.