This paper presents a fully automatic model-driven technique to generate test cases for graphical user interfaces (GUIs)-based applications. The technique uses feedback from the execution of a ??seed test suite,?? which is generated automatically using an existing structural event interaction graph model of the GUI. During its execution, the runtime effect of each GUI event on all other events pinpoints event semantic interaction (ESI) relationships, which are used to automatically generate new test cases. Two studies on eight applications demonstrate that the feedback-based technique 1) is able to significantly improve existing techniques and helps identify serious problems in the software and 2) the ESI relationships captured via GUI state yield test suites that most often detect more faults than their code, event, and event-interaction-coverage equivalent counterparts.