Virtual DOM Coverage: Drive an Effective Testing for Dynamic Web Applications

Test adequacy criteria are fundamental in software testing. Among them, code coverage criterion is widely used due to its simplicity and effectiveness. However, in dynamic web application testing, merely covering server-side script code is inadequate because it neglects client-side execution, which plays an important role in triggering client-server interactions to reach important execution states. Similarly, a criterion aiming at covering the UI elements on client-side pages ignores the server-side execution, leading to insufficiency. In this paper, we propose Virtual DOM (V-DOM) Coverage, a novel criterion, to drive web application testing. With static analysis, we first aggregate all the DOM objects that may be produced by a piece of server script to construct a V-DOM tree. The tree models execution on both the clientand server-sides such that V-DOM coverage is more effective than existing coverage criteria in web application testing. We conduct an empirical study on five real world dynamic web applications. We find that V-DOM tree can model much more DOM objects than a web crawling based technique. Test selection based on V-DOM tree criterion substantially outperforms the existing code coverage and UI element coverage, by detecting more faults.