Using Petri Nets to Test Concurrent Behavior of Web Applications

Web applications are used by companies across the world to deploy their products and services. Because of the technologies used to build web applications, they are by nature concurrent, for example, multiple users can have problems when accessing the same limited resources. The combination of the stateless nature of web applications and concurrent behavior creates unique challenges. Models have traditionally been used to test specific aspects of systems. However, existing web application models do not effectively address the combination of concurrent behavior and stateless protocol. This research project is using a novel Petri net-based model for web applications. This paper defines a novel way to design model-based coverage criteria tests that address concurrent behavior involving HTTP browser-based sessions. A tool that extracts the Petri net model of a web application has been developed and used to study ten web applications totaling 17,535 lines of code. The tool was used to extract the model and generate tests, revealing 36 naturally occurring software faults that had not been found during previous testing.