Smartphones and other mobile devices are increasingly changing the way people pay. What looks like a simple payment process from the outside or for the customer, however, is a complex ecosystem with various players behind the scenes. These players are TSM providers, MNOs, handset and card reader manufacturers, and many others. To make sure that the processes in this vast infrastructure run smoothly, all individual components as well as their interactions must be tested carefully. For mobile payment, interoperability is key.