How do I got about mocking UIApplication.sharedApplication to test shortcutItems?

I'm trying to write XCTests for my 3D Touch code for quick actions (when you 3D Touch on the icon and launch the app). However, I can't seem to figure out a good way to write a protocol that would allow me to mock UIApplication.sharedApplication() so that, when the tests are running and that is called, the test data goes to the mock class instead of the actual shortcutItems. Any suggestions?

Originally I was thinking

protocol MockShortcutItems {
  var shortcutItems: [UIApplicationShortcutItem] { get set }
}

extension UIApplication: MockShortcutItems {}