I couldn't agree more. I am doing a lot of nodejs development these days and it's usually a pain to verify that the code works the way it should. Writing a quick bunch of unit tests is very superior to loading your code in an interactive console and manually fiddling with inputs / outputs. These unit tests often break at the first refactoring and we rewrite them at that point. I'm a bit surprised that people argue that unit tests facilitate "aggressive" refactorings. Aggressive refactoring to me means architecture changes and unit tests almost never survive those. Integration testing is what ensures proper functioning in those situations for me.