ZF-3145: Zend_Controller_Front::resetInstance() doesn't reset helpers which are stored in static variable.
I have find this bug when writing unit tests. After resetting front controller, redirector helper still existed, with all redirection params set earlier. I had to manually reset redirector before every test.
In my opinion when resetting FrontControllers all helpers should be cleared too\ - this would help much in unit testing of controllers.