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

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

import '../support/test_app.dart';

void main() {
  /// Pumps [child] under a screen tint, in a medium window, so a gradient
  /// in it claims its colour while in view.
  Future<ScreenTint> show(WidgetTester tester, {required bool visible}) async {
    tester.view.physicalSize = const Size(800, 600);
    tester.view.devicePixelRatio = 1;
    addTearDown(tester.view.reset);
    final tint = ScreenTint();
    addTearDown(tint.dispose);
    await tester.pumpWidget(
      testApp(
        ScreenTintScope(
          notifier: tint,
          child: TabVisibility(
            visible: visible,
            child: const TopGradient(
              color: Color(0xFFBA1E55),
              background: Color(0xFFFFFFFF),
              child: SizedBox.expand(),
            ),
          ),
        ),
      ),
    );
    await tester.pump();
    return tint;
  }

  testWidgets('a screen whose tab shows gives the frame its colour', (
    tester,
  ) async {
    final tint = await show(tester, visible: true);

    expect(tint.color, const Color(0xFFBA1E55));
  });

  testWidgets("a hidden tab's screen leaves the frame's colour alone", (
    tester,
  ) async {
    final tint = await show(tester, visible: false);

    expect(tint.color, Brand.primary);
  });

  testWidgets('outside any tabs, a screen counts as shown', (tester) async {
    late bool visible;
    await tester.pumpWidget(
      Builder(
        builder: (context) {
          visible = TabVisibility.of(context);
          return const SizedBox();
        },
      ),
    );

    expect(visible, isTrue);
  });

  testWidgets('the tabs stack shows the tab chosen, keeps the others alive, '
      'and tells each whether it shows', (tester) async {
    final visible = <String, bool>{};
    Widget tab(String name) => Builder(
      builder: (context) {
        visible[name] = TabVisibility.of(context);
        return Text(name);
      },
    );
    await tester.pumpWidget(
      testApp(TabsStack(index: 1, children: [tab('Home'), tab('Maps')])),
    );

    expect(find.text('Maps'), findsOneWidget);
    expect(find.text('Home'), findsNothing, reason: 'offstage');
    expect(find.text('Home', skipOffstage: false), findsOneWidget);
    expect(visible, {'Home': false, 'Maps': true});
  });
}