A method, computer program product, and computer system for receiving, by a computing device, a selection of one or more files for which to have one or more automated unit tests generated for an application under test. An action in the application under test is received while the application under test is used. Behavior data of how the application under test responds to the action is tracked, wherein tracking is performed by inserting observer code using aspect oriented programming method, which tracks each method's interaction with its own objects and objects that are passed to it. An automated unit test of the one or more automated unit tests is generated for underlying code of the application under test invoked when receiving the action based upon, at least in part, the behavior data of how the application under test responds to the action.