Mobile applications (apps) are being widely used around the world. The long-term success and diffusion of a mobile app depends on it being well-tested, with respect to its performance and its reliability. Mobile app testing is typically carried out in multiple stages. An app is first tested for performance and reliability in a controlled lab-like environment during its development. However, the heterogeneity of in-the-field environments (including many device profiles, network speeds, etc.) is far greater than in a lab setting, with a small group of users. For this reason, a so-called Beta version of the app is typically rolled-out to a limited number of users, to get deeper insights into its performance and reliability in the field. After the Beta test results are analyzed, and refinements are incorporated, the application is released to all of its intended users. However, this work is based on a belief that field testing should be an automatic and ongoing process. Field test data, representing the actual performance and reliability of the app in the field, should be continuously fed back to the developer. To accomplish this, this paper proposes a framework for ongoing monitoring and field testing of mobile apps. This framework includes a library that mobile app developers can use to collect performance and reliability data during ongoing extensive field testing. These data are collected and presented using a web form to inform developers about the performance and reliability of their apps as they are being used by end-users in the field.