Unfortunately Sebastian Bergmann decided to remove PHPUnit_Story from future PHPUnit versions. Thanks to elvan for pointing me to the relevant comment. As an alternative Behat has been suggested but it seems too bloated for me TBH. There is also PHPSpec but it's non flexible enough for me and tightly bound with English language (What's the purpose of using DSL if customers can't speak English). Since both frameworks are quite young I think I'll just stick to PHPUnit and see what's going on on the BDD frameworks arena. Even PHPUnit_Story parts of this entry are going to be deprecated soon, rest is still valid! When doing TDD, please write tests with design and behaviour of application in mind instead of testing single functions.
If you are lucky enough and have the privilege to develop on a Linux based environment, this little tip might boost-up your TDD process (at least the Unit Testing part). Please note, that this should work just fine with Apple computers also, but not tested!