I released the new great Module::Spy. Repository is now on github.com/tokuhirom/Module-Spy.git. I saw jasmine at few days ago. jasmine is very popular BDD testing framework for JavaScript. jasmine has the great interface for spy. A spy can stub any function and tracks calls to it and all arguments. I'm using the local feature in the past days. Because it's good enough for me. For example, followin