This is the sample application that I modified during my talk for XDC 2018:
Factoring your application for testability
It is based on the sample Xojo application "ToDoDesktop".
The presentation itself is included as a PDF inside the "Factoring for testability" folder.
If you are looking for the XDC 2016 version of this app, look for the tag "xdc-2016"
https://github.com/philippec-ls/TaskMaster/releases/tag/xdc-2016