testWidgets('FocusScope descendantsAreFocusable', (WidgetTester tester) async {
    final focusScopeNode = FocusScopeNode();
    await tester.pumpWidget(
      FocusScope(
        node: focusScopeNode,
        child: const SizedBox.shrink(),
      ),
    );
    expect(focusScopeNode.descendantsAreFocusable, isTrue);

    focusScopeNode.canRequestFocus = false;
    expect(focusScopeNode.descendantsAreFocusable, isFalse);
 
    focusScopeNode.canRequestFocus = true;
    expect(focusScopeNode.descendantsAreFocusable, isTrue);

    // Disabling canRequestFocus and updating the widget will permanently disable descendantsAreFocusable.
    focusScopeNode.canRequestFocus = false;

    // After this pump, setting canRequestFocus back will not restore
    // descendantsAreFocusable to true.
    await tester.pumpWidget(
      FocusScope(
        node: focusScopeNode,
        child: const SizedBox.shrink(),
      ),
    );

    focusScopeNode.canRequestFocus = true;

    // Test failure:
    // This should be back to true, but in FocusNode state didUpdateWidget the 
    // descendantsAreFocusable on the focusScopeNode got set to false.
    expect(focusScopeNode.descendantsAreFocusable, isTrue);
  });