Testing Graphical User Interfaces (GUI) is a difficult problem because the GUI possesses a large number of states to be tested; the input space is extremely large due to different permutations of inputs and events, which affect the GUI, and complex GUI dependencies, which may exist. There has been little systematic study of this problem yielding a resulting strategy, which is effective and scalable. The proposed method concentrates upon user sequences of GUI objects and selections, which collaborate, called complete interaction sequences (CIS) that produce a desired response for the user. A systematic method to test these CIS utilizes a finite-state model to generate tests. Identifying components of the CIS that can be tested separately can substantially reduce the required tests. Since consideration is given to defects totally within each CIS, and the components reduce required testing further, this approach is scalable. An empirical investigation of this method shows that substantial reduction in tests can still detect the defects in the GUI. Future research will prioritize testing related to the CIS testing for maximum benefit if testing time is limited.