It is useful to know these VoiceOver gestures to activate/deactivate Screen Curtain, pause/resume VoiceOver, easily simulate a long press for opening context menus, or quickly move the cursor to the screen's first or last elements.

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This is my favorite way of testing VoiceOver. Pick a flow in your app. Turn VoiceOver on. Triple tap with three fingers on the screen to enable Screen Curtain. The screen goes off but you can still navigate your device with VoiceOver.

VoiceOver has a very cool gesture called the Magic Tap (double tap with two fingers). It should execute the most important task for the current state of the app. Examples: start/stop timer, play/pause music, take a photo, compose a tweet... You just need to override accessibilityPerformMagicTap() to capture that gesture, execute the desired code, and return true if handled successfully. https://developer.apple.com/documentation/objectivec/nsobject-swift.class/accessibilityperformmagictap()

Support both orientations, if possible. I know not even iOS itself does it, but it hasn't always been like that. You'll create a more robust UI that will be easier to port to iPadOS. And especially, don't force your users to rotate their devices.