A Graphical User Interface (GUI) is the most widely used method whereby information systems interact with users. According to ACM Computing Surveys, on average, more than 45% of software code in a software application is dedicated to the GUI. However, GUI testing is extremely expensive. In unit testing, 10,000 cases can often be automatically tested within a minute whereas, in GUI testing, 10,000 simple GUI test cases need more than 10 hours to complete. This thesis effectively addresses the challenges of existing GUI testing methods and provides a unified solution to GUI testing automation. The three main contributions of this thesis are the proposal of the Graphic User Interface Testing Automation Model
 (GUITAM), the development of GUI Defect Classification and the proposal of the Long Use Case Closure Envelope Model.