We have released new documentation: "ShrinkTheWeb Integration Testing Guide"

This guide lays out a foundation for "Best Practices", reviews some goals of integration, and covers all recommended tests that should be performed to ensure stable and efficient integration.

That is all covered in the "Baseline Testing" and then there is a second section devoted to 3rd-party integrators that covers things like: User Interface (UI), Integration of Account API, and test cases that should be handled for a more public-use friendly integration.

Check the code documentation for details.