Applying Model-based Testing to HTML Rendering Engines - A Case Study

Conformance testing is a widely used approach to validate a system correct w.r.t. its specification. This approach is mainly used for behavior-oriented systems. BAiT (Behavior Adaptation in Testing) is a conformance testing approach for data-intensive reactive systems. In this paper, we validate the applicability of BAiT to systems, which are not behavior-oriented (reactive) but document-centered. In particular, we apply BAiT to the test of the HTML rendering engine Gecko, which is used by Mozilla Firefox. In order to do so, we formally specify a part of the CSS box model in the specification language µCRL and implement a wrapper for the Gecko renderer. Then, we automatically generate test cases and run tests with BAiT in a controlled experiment in order to demonstrate our approach on the relevant part of Gecko.