1. A method comprising, by one or more computer systems: dynamically crawling an event-driven application in a plurality of client-tier environments; for each of the client-tier environments, generating a behavioral model of the event-driven application based on the dynamic crawling; for each of the behavioral models, determining one or more pairwise equivalences with respect to one or more other ones of the behavioral models; 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.