The Android system provides various mechanisms for interactions between apps, of which the exported activity is an activity that can be launched by other apps during runtime without complex inter-process communication. Most of the existing works on testing Android apps mainly focus on the functionalities bound to the GUI components in the app, while the app often does not include the GUI callbacks to activate its exported activities. This study proposes a method to systematically test the exported activities in the way of generating a set of agent apps as test drivers to launch these activities. It first statically analyzes the APK file to figure out the exported activities and extract the keys and types of their required data items, and then fills this corresponding data to a pre-set template to build the test drivers. All these proposed techniques are implemented into a prototype tool called EASTER. The preliminary experiments on several real-world apps show that without comprehensive testing, some exported activities are vulnerable to various external apps launches.