Well, it was bound to happen sooner or later. Apple has officially sent me a cease and desist letter to take down my host of the XCTest Documentation.
But that's OK! I was only hosting the docs because Apple wasn't doing it themselves. To be honest, I expected this day to come sooner.
Earlier this year Apple updated their API Reference and finally added official XCTest support. Apple's XCTest documentation is available alongside their other API References.
To all of those that linked here, thank you! I hope it helped get your XCUITest suite up and running.