halkyon/packages/halkyon_ui/test/widget/scroll_hiding_fab_test.dart

import 'package:flutter_test/flutter_test.dart';
import 'package:halkyon_ui/halkyon_ui.dart';
import 'package:material_ui/material_ui.dart';

void main() {
  /// A list of [lines] with a button that hides while reading onwards.
  Future<void> show(
    WidgetTester tester, {
    int lines = 100,
    bool pinned = false,
  }) async {
    tester.view.physicalSize = const Size(400, 800);
    tester.view.devicePixelRatio = 1;
    addTearDown(tester.view.reset);
    await tester.pumpWidget(
      MaterialApp(
        home: ScrollHidingFab(
          pinned: pinned,
          builder: (context, fab) => Scaffold(
            floatingActionButton: fab,
            body: ListView(
              children: [
                for (var i = 0; i < lines; i++)
                  SizedBox(height: 48, child: Text('Line $i')),
              ],
            ),
          ),
          fab: FloatingActionButton(
            tooltip: 'New studyset',
            onPressed: () {},
            child: const Icon(Icons.add),
          ),
        ),
      ),
    );
  }

  Finder fab() => find.byTooltip('New studyset').hitTestable();

  testWidgets('hides while scrolling down and returns when scrolling up', (
    tester,
  ) async {
    await show(tester);
    expect(fab(), findsOneWidget);

    await tester.drag(find.byType(ListView), const Offset(0, -300));
    await tester.pumpAndSettle();
    expect(fab(), findsNothing);

    await tester.drag(find.byType(ListView), const Offset(0, 100));
    await tester.pumpAndSettle();
    expect(fab(), findsOneWidget);
  });

  testWidgets('stays when the list fits without scrolling', (tester) async {
    await show(tester, lines: 3);

    await tester.drag(find.byType(ListView), const Offset(0, -300));
    await tester.pumpAndSettle();

    expect(fab(), findsOneWidget);
  });

  testWidgets('stays while pinned, as a field being written in', (
    tester,
  ) async {
    await show(tester, pinned: true);

    await tester.drag(find.byType(ListView), const Offset(0, -300));
    await tester.pumpAndSettle();

    expect(fab(), findsOneWidget);
  });
}