One of the great difficulties of Facebook application development is the difficulty in running large-scale tests due to the large number of Facebook accounts required, and the Facebook Terms of Use which does not allow automated systems to access the Facebook servers. These issues are explained in depth in Load testing Facebook apps (Part 1) and Load testing Facebook apps (Part 2). FriendRunner acts as a drop-in replacement for the Facebook servers, and so allows you to run your tests with as many users as you'd like. Furthermore, FriendRunner's automated test system runs the entire test for you once you create a test script to define the actions for a single user.