Dynodroid: An Input Generation System for Android Apps

We present a system Dynodroid for generating relevant inputs to unmodified Android apps. Dynodroid views an app as an event-driven program that interacts with its environment by means of a sequence of events through the Android framework. By instrumenting the framework once and for all, Dynodroid monitors the reaction of an app upon each event in a lightweight manner, using it to guide the generation of the next event to the app. Dynodroid also allows interleaving events from machines, which are better at generating a large number of simple inputs, with events from humans, who are better at providing intelligent inputs. We evaluated Dynodroid on 50 open-source Android apps, and compared it with two prevalent approaches: users manually exercising apps, and Monkey, a popular fuzzing tool. Dynodroid, humans, and Monkey covered 55%, 60%, and 53%, respectively, of each app’s Java source code on average. Monkey took 20X more events on average than Dynodroid. Dynodroid also found 9 bugs in 7 of the 50 apps, and 6 bugs in 5 of the top 1,000 free apps on Google Play. 1