Declarative layout constraints for testing web applications

• The paper introduces a logical language for detecting layout bugs in web applications.
• It describes an automated testing tool to verify such properties.
• It shows how counter-examples can be generated when a violation occurs.

The paper focuses on bugs in web applications that can be detected by analyzing the contents and layout of page elements inside a browser's window. Based on an empirical analysis of 35 real-world web sites and applications (such as Facebook, Dropbox, and Moodle), it provides a survey and classification of more than 90 instances of layout-based bugs. It then introduces Cornipickle, an automated testing tool that provides a declarative language to express desirable properties of a web application as a set of human-readable assertions on the page's HTML and CSS data. Such properties can be verified on-the-fly as a user interacts with an application.