Another nice aspect of test driven development: you can code nice nuggets of usable code. If you have the tests assuring everything is stable, you can — and should — commit often. I find it efficient and effective designing my workload around this, aiming to add just one new piece of useful functionality. Never more than a spot. (Or something may happen, you never know what.)
It keeps the code simple in your head. Complexity kills. Simplicity rules. And keeping it simple means it doesn’t take too long, so it isn’t an imposition on your life. And so it is with revision 175 of the forces.forms javscript library, introducing initial support for custom form validation (based on setCustomValidity from the HTML 5 spec).
And truly, that’s enough for a light coding session.