For example, the mobile app launches the sumup app using sumup custom URL scheme, then I execute a fake transaction without sumup device and then the sumup application triggers success callback (which will open the mobile app using my app custom URL scheme and navigate to the appropriate view)?
It seems that there is no way to do this without making a real transaction with the real device.
There is no such functionality atm. If you need to test your integration feel free to get in touch with integration@sumup.com and explain your setup. We'll do our best to get you started.
For example, the mobile app launches the sumup app using sumup custom URL scheme, then I execute a fake transaction without sumup device and then the sumup application triggers success callback (which will open the mobile app using my app custom URL scheme and navigate to the appropriate view)? It seems that there is no way to do this without making a real transaction with the real device.
Thanks