copy of my comment: I am python developer. I also ask myself these questions, and on current project I use TDD heavily (but still far from 100%). One thing it

copy of my comment: I am python developer. I also ask myself these questions, and on current project I use TDD heavily (but still far from 100%). One thing it totally gives me is ability to let other devs in team without need of tons of collaboration to implement some functionality, and then for me being able to refactor it as much as I want, but not being blamed for errors. Since it's their job to put as much tests as would cover all functionality, and it's my job to only write tests for my new code, and fix (or remove) old tests. I think this blame-less in dynamic languages like python is real diamond :) Also, one question I ask myself is "unit-testing vs type theory". And can unit-testing in dynamic language be an instrument that would make dynamic type-checking to be a good thing even in serious production. It's also a big question, and there's a lot to think on it.