At Plurk.com we use automated testing, but we don't develop by the TDD principle or do unit testing - as it's really hard to do with lots of code and lots of di

At Plurk.com we use automated testing, but we don't develop by the TDD principle or do unit testing - as it's really hard to do with lots of code and lots of diversity (e.g. MySQL, JavaScript, Python, different layers of caching, Mako templates, Erlang etc.). We test the core functionality and cover things that 80% of users would use. This has worked ok so far without too many bugs - even thought we deploy new versions each day.