1. A method comprising, by one or more computer systems: upon identification by a user of an event-driven application, automatically and without further user interaction dynamically crawling the event-driven application in a plurality of client-tier environments, wherein dynamically crawling comprises automatically and without user-interaction exercising code to detect and execute one or more doorways of the event-driven application in the plurality of client-tier environments; for each of the client-tier environments, generating a behavioral model of the event-driven application comprising rooted directed graphs based on the dynamic crawling; for each of the behavioral model, determining one or more pairwise equivalences with respect to one or more other ones of the behavioral models, wherein determining the one or more pairwise equivalences comprises determining isomorphism between the rooted directed graphs; and for each of the client-tier environments, determining one or more differences in an end-user experience of the event-driven application in the client-tier environment with respect to one or more other end-user experiences of the event-driven application in one or more other ones of the client-tier environments.