Say one has a structural codebase where lots of the code is in GUI control events and has no tests. So such code, to my knowledge is not suitable for unit testing Is there a tool that can test each routine automatically replacing references to code elements external to the routine (be they functions, variables or GUI controls) with appropriate mocks(?) and record the results in a database for later comparison after code changes? So the testing program would have the duty of writing, running and reporting tests with minimal intervention?