In recent years, Web applications have grown rapidly. As Web applications become complex, there is a growing concern about their quality and reliability. In this paper, we present a methodology that uses an Object-Oriented Web Test Model (WTM) to support Web application testing. The test model captures both structural and behavioral test artifacts of Web applications and represents the artifacts form the object, behavior, and structure perspectives. Based on the test model, both structural and behavioral test cases can be derived automatically to ensure the quality of Web applications. Moreover, the model also can be used as a road map to identify change ripple effects and to find cost-effective testing strategies for reducing test efforts required in the regression testing.