Many testing and analysis techniques have been developed for inhouse use. Although they are effective at discovering defects before a program is deployed, these techniques are often limited due to the complexity of real-world code and thus miss program faults. It will be the users of the program who eventually experience failures caused by the undetected faults. To take advantage of the large number of program runs carried by the users, recent work has proposed techniques to collect execution profiles from the users for developers to perform post-deployment failure analysis. However, in order to protect users' privacy and to reduce run-time overhead, such profiles are usually not detailed enough for the developers to identify or fix the root causes of the failures. In this paper, we propose a novel approach to utilize user execution profiles for more effective in-house testing and analysis. Our key insight is that execution profiles for program failures can be used to simplify a ...