NavigationStack and TabView have inadequate automated testing

[dfabulich]

NavigationStack and TabView are incredibly complicated pieces of code; it's extremely difficult to touch them without accidentally breaking something.

skip-ui has some automated tests, but no automated tests of these areas. We should fix that, ideally not (merely) by adding automated tests to https://github.com/skiptools/skipapp-showcase but adding tests that run during the skip-ui CI.

[dfabulich]

There are a lot of open questions about how this might be best accomplished.

• Would these be tests that run on iOS and Android?
  • If so, what cross-platform testing library would we use?
    • Marc mentioned preferring something higher-level like Maestro.
    • I think I'd prefer XCUIAutomation Add support for XCUIAutomation skip#649
  • But perhaps we shouldn't. skip-ui runs on Android only, and maybe we'd be better off with Android-only behavior UI tests. There are a lot of ways to do that, too. https://developer.android.com/training/testing/ui-tests/behavior
    • Compose testing API? https://developer.android.com/develop/ui/compose/testing
    • UI Automator? https://developer.android.com/training/testing/ui-automator
    • Compose Preview Screenshot Testing? Add support for Compose Preview Screenshot Testing skip#586
• What device should the tests run on?
  • Robolectric?
  • Or an emulator?
    • Which emulated device? (Multiple devices??)
    • How would the emulated device be set up, managed, and launched?
      • Build-managed devices? https://developer.android.com/studio/test/managed-devices
• Would we want to have different answers for these questions for skip-ui vs end-user apps like skipapp-showcase?

It's not totally clear to me how we'd begin to answer any of these questions.

(Another wrinkle: I think we'd want to test that layout shifts aren't happening, which sounds pretty thorny to me.)

Maybe we could do a bake-off or something? Or maybe @marcprux just picks an approach?