Abstract. Society increasingly depends on web applications for business, work, and pleasure. As the use of web applications continues to increase, the number of failures, some minor and some major, continues to grow. A significant problem is that we still have relatively weak abilities to test web applications, and often rely on informal, ad-hoc, and ineffective techniques. A key driver to this problem is that web applications use novel technologies, including control structures that are not available in traditional software, and new state handling techniques, including new variable scopes. Traditional testing techniques do not adequately model or test these novel technologies. The atomic section model (ASM), which was introduced in a previous paper, models these novel technologies to support design, analysis, and testing. This paper presents an empirical study to evaluate the effectiveness of the ASM to design tests. The model was implemented into a tool, WASP, which extracts the ASM from the implementation and supports various test criteria. We studied ten web applications, totaling 156 components and 11,829 lines of code. Using WASP, we generated 207 tests, which revealed 31 faults. Seventeen of those faults exposed internal information about the application and server.