packages/flutter/test/material/page_transitions_theme_test.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/services.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  final TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized();

  testWidgets('Default PageTransitionsTheme platform', (WidgetTester tester) async {
    await tester.pumpWidget(const MaterialApp(home: Text('home')));
    final PageTransitionsTheme theme = Theme.of(tester.element(find.text('home'))).pageTransitionsTheme;
    expect(theme.builders, isNotNull);
    for (final TargetPlatform platform in TargetPlatform.values) {
      switch (platform) {
        case TargetPlatform.android:
        case TargetPlatform.iOS:
        case TargetPlatform.macOS:
          expect(
            theme.builders[platform],
            isNotNull,
            reason: 'theme builder for $platform is null',
          );
        case TargetPlatform.fuchsia:
        case TargetPlatform.linux:
        case TargetPlatform.windows:
          expect(
            theme.builders[platform],
            isNull,
            reason: 'theme builder for $platform is not null',
          );
      }
    }
  });

  testWidgets('Default PageTransitionsTheme builds a CupertinoPageTransition', (WidgetTester tester) async {
    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
      '/': (BuildContext context) => Material(
        child: TextButton(
          child: const Text('push'),
          onPressed: () { Navigator.of(context).pushNamed('/b'); },
        ),
      ),
      '/b': (BuildContext context) => const Text('page b'),
    };

    await tester.pumpWidget(
      MaterialApp(
        routes: routes,
      ),
    );

    expect(Theme.of(tester.element(find.text('push'))).platform, debugDefaultTargetPlatformOverride);
    expect(find.byType(CupertinoPageTransition), findsOneWidget);

    await tester.tap(find.text('push'));
    await tester.pumpAndSettle();
    expect(find.text('page b'), findsOneWidget);
    expect(find.byType(CupertinoPageTransition), findsOneWidget);
  }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));

  testWidgets('Default PageTransitionsTheme builds a _ZoomPageTransition for android', (WidgetTester tester) async {
    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
      '/': (BuildContext context) => Material(
        child: TextButton(
          child: const Text('push'),
          onPressed: () { Navigator.of(context).pushNamed('/b'); },
        ),
      ),
      '/b': (BuildContext context) => const Text('page b'),
    };

    await tester.pumpWidget(
      MaterialApp(
        routes: routes,
      ),
    );

    Finder findZoomPageTransition() {
      return find.descendant(
        of: find.byType(MaterialApp),
        matching: find.byWidgetPredicate((Widget w) => '${w.runtimeType}' == '_ZoomPageTransition'),
      );
    }

    expect(Theme.of(tester.element(find.text('push'))).platform, debugDefaultTargetPlatformOverride);
    expect(findZoomPageTransition(), findsOneWidget);

    await tester.tap(find.text('push'));
    await tester.pumpAndSettle();
    expect(find.text('page b'), findsOneWidget);
    expect(findZoomPageTransition(), findsOneWidget);
  }, variant: TargetPlatformVariant.only(TargetPlatform.android));

  testWidgets('PageTransitionsTheme override builds a _OpenUpwardsPageTransition', (WidgetTester tester) async {
    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
      '/': (BuildContext context) => Material(
        child: TextButton(
          child: const Text('push'),
          onPressed: () { Navigator.of(context).pushNamed('/b'); },
        ),
      ),
      '/b': (BuildContext context) => const Text('page b'),
    };

    await tester.pumpWidget(
      MaterialApp(
        theme: ThemeData(
          pageTransitionsTheme: const PageTransitionsTheme(
            builders: <TargetPlatform, PageTransitionsBuilder>{
              TargetPlatform.android: OpenUpwardsPageTransitionsBuilder(), // creates a _OpenUpwardsPageTransition
            },
          ),
        ),
        routes: routes,
      ),
    );

    Finder findOpenUpwardsPageTransition() {
      return find.descendant(
        of: find.byType(MaterialApp),
        matching: find.byWidgetPredicate((Widget w) => '${w.runtimeType}' == '_OpenUpwardsPageTransition'),
      );
    }

    expect(Theme.of(tester.element(find.text('push'))).platform, debugDefaultTargetPlatformOverride);
    expect(findOpenUpwardsPageTransition(), findsOneWidget);

    await tester.tap(find.text('push'));
    await tester.pumpAndSettle();
    expect(find.text('page b'), findsOneWidget);
    expect(findOpenUpwardsPageTransition(), findsOneWidget);
  }, variant: TargetPlatformVariant.only(TargetPlatform.android));

  testWidgets('PageTransitionsTheme override builds a CupertinoPageTransition on android', (WidgetTester tester) async {
    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
      '/': (BuildContext context) => Material(
        child: TextButton(
          child: const Text('push'),
          onPressed: () { Navigator.of(context).pushNamed('/b'); },
        ),
      ),
      '/b': (BuildContext context) => const Text('page b'),
    };

    await tester.pumpWidget(
      MaterialApp(
        theme: ThemeData(
          pageTransitionsTheme: const PageTransitionsTheme(
            builders: <TargetPlatform, PageTransitionsBuilder>{
              TargetPlatform.android: CupertinoPageTransitionsBuilder(),
            },
          ),
        ),
        routes: routes,
      ),
    );

    expect(Theme.of(tester.element(find.text('push'))).platform, debugDefaultTargetPlatformOverride);
    expect(find.byType(CupertinoPageTransition), findsOneWidget);

    await tester.tap(find.text('push'));
    await tester.pumpAndSettle();
    expect(find.text('page b'), findsOneWidget);
    expect(find.byType(CupertinoPageTransition), findsOneWidget);
  }, variant: TargetPlatformVariant.only(TargetPlatform.android));

  testWidgets('CupertinoPageTransition on android does not block gestures on backswipe', (WidgetTester tester) async {
    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
      '/': (BuildContext context) => Material(
        child: TextButton(
          child: const Text('push'),
          onPressed: () { Navigator.of(context).pushNamed('/b'); },
        ),
      ),
      '/b': (BuildContext context) => const Text('page b'),
    };

    await tester.pumpWidget(
      MaterialApp(
        theme: ThemeData(
          pageTransitionsTheme: const PageTransitionsTheme(
            builders: <TargetPlatform, PageTransitionsBuilder>{
              TargetPlatform.android: CupertinoPageTransitionsBuilder(),
            },
          ),
        ),
        routes: routes,
      ),
    );

    expect(Theme.of(tester.element(find.text('push'))).platform, debugDefaultTargetPlatformOverride);
    expect(find.byType(CupertinoPageTransition), findsOneWidget);

    await tester.tap(find.text('push'));
    await tester.pumpAndSettle();
    expect(find.text('page b'), findsOneWidget);
    expect(find.byType(CupertinoPageTransition), findsOneWidget);

    await tester.pumpAndSettle(const Duration(minutes: 1));

    final TestGesture gesture = await tester.startGesture(const Offset(5.0, 100.0));
    await gesture.moveBy(const Offset(400.0, 0.0));
    await gesture.up();
    await tester.pump();

    await tester.pumpAndSettle(const Duration(minutes: 1));

    expect(find.text('push'), findsOneWidget);
    await tester.tap(find.text('push'));
    await tester.pumpAndSettle();
    expect(find.text('page b'), findsOneWidget);
  }, variant: TargetPlatformVariant.only(TargetPlatform.android));

  testWidgets('PageTransitionsTheme override builds a _FadeUpwardsTransition', (WidgetTester tester) async {
    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
      '/': (BuildContext context) => Material(
        child: TextButton(
          child: const Text('push'),
          onPressed: () { Navigator.of(context).pushNamed('/b'); },
        ),
      ),
      '/b': (BuildContext context) => const Text('page b'),
    };

    await tester.pumpWidget(
      MaterialApp(
        theme: ThemeData(
          pageTransitionsTheme: const PageTransitionsTheme(
            builders: <TargetPlatform, PageTransitionsBuilder>{
              TargetPlatform.android: FadeUpwardsPageTransitionsBuilder(), // creates a _FadeUpwardsTransition
            },
          ),
        ),
        routes: routes,
      ),
    );

    Finder findFadeUpwardsPageTransition() {
      return find.descendant(
        of: find.byType(MaterialApp),
        matching: find.byWidgetPredicate((Widget w) => '${w.runtimeType}' == '_FadeUpwardsPageTransition'),
      );
    }

    expect(Theme.of(tester.element(find.text('push'))).platform, debugDefaultTargetPlatformOverride);
    expect(findFadeUpwardsPageTransition(), findsOneWidget);

    await tester.tap(find.text('push'));
    await tester.pumpAndSettle();
    expect(find.text('page b'), findsOneWidget);
    expect(findFadeUpwardsPageTransition(), findsOneWidget);
  }, variant: TargetPlatformVariant.only(TargetPlatform.android));

  Widget boilerplate({
    required bool themeAllowSnapshotting,
    bool secondRouteAllowSnapshotting = true,
  }) {
    return MaterialApp(
      theme: ThemeData(
        useMaterial3: true,
        pageTransitionsTheme: PageTransitionsTheme(
          builders: <TargetPlatform, PageTransitionsBuilder>{
            TargetPlatform.android: ZoomPageTransitionsBuilder(
              allowSnapshotting: themeAllowSnapshotting,
            ),
          },
        ),
      ),
      onGenerateRoute: (RouteSettings settings) {
        if (settings.name == '/') {
          return MaterialPageRoute<Widget>(
            builder: (_) => const Material(child: Text('Page 1')),
          );
        }
        return MaterialPageRoute<Widget>(
          builder: (_) => const Material(child: Text('Page 2')),
          allowSnapshotting: secondRouteAllowSnapshotting,
        );
      },
    );
  }

  bool isTransitioningWithSnapshotting(WidgetTester tester, Finder of) {
    final Iterable<Layer> layers = tester.layerListOf(
      find.ancestor(of: of, matching: find.byType(SnapshotWidget)).first,
    );
    final bool hasOneOpacityLayer = layers.whereType<OpacityLayer>().length == 1;
    final bool hasOneTransformLayer = layers.whereType<TransformLayer>().length == 1;
    // When snapshotting is on, the OpacityLayer and TransformLayer will not be
    // applied directly.
    return !(hasOneOpacityLayer && hasOneTransformLayer);
  }

  testWidgets('ZoomPageTransitionsBuilder default route snapshotting behavior', (WidgetTester tester) async {
    await tester.pumpWidget(
      boilerplate(themeAllowSnapshotting: true),
    );

    final Finder page1 = find.text('Page 1');
    final Finder page2 = find.text('Page 2');

    // Transitioning from page 1 to page 2.
    tester.state<NavigatorState>(find.byType(Navigator)).pushNamed('/2');
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 50));

    // Exiting route should be snapshotted.
    expect(isTransitioningWithSnapshotting(tester, page1), isTrue);

    // Entering route should be snapshotted.
    expect(isTransitioningWithSnapshotting(tester, page2), isTrue);

    await tester.pumpAndSettle();

    // Transitioning back from page 2 to page 1.
    tester.state<NavigatorState>(find.byType(Navigator)).pop();
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 50));

    // Exiting route should be snapshotted.
    expect(isTransitioningWithSnapshotting(tester, page2), isTrue);

    // Entering route should be snapshotted.
    expect(isTransitioningWithSnapshotting(tester, page1), isTrue);
  }, variant: TargetPlatformVariant.only(TargetPlatform.android), skip: kIsWeb); // [intended] rasterization is not used on the web.

  testWidgets('ZoomPageTransitionsBuilder.allowSnapshotting can disable route snapshotting', (WidgetTester tester) async {
    await tester.pumpWidget(
      boilerplate(themeAllowSnapshotting: false),
    );

    final Finder page1 = find.text('Page 1');
    final Finder page2 = find.text('Page 2');

    // Transitioning from page 1 to page 2.
    tester.state<NavigatorState>(find.byType(Navigator)).pushNamed('/2');
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 50));

    // Exiting route should not be snapshotted.
    expect(isTransitioningWithSnapshotting(tester, page1), isFalse);

    // Entering route should not be snapshotted.
    expect(isTransitioningWithSnapshotting(tester, page2), isFalse);

    await tester.pumpAndSettle();

    // Transitioning back from page 2 to page 1.
    tester.state<NavigatorState>(find.byType(Navigator)).pop();
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 50));

    // Exiting route should not be snapshotted.
    expect(isTransitioningWithSnapshotting(tester, page2), isFalse);

    // Entering route should not be snapshotted.
    expect(isTransitioningWithSnapshotting(tester, page1), isFalse);
  }, variant: TargetPlatformVariant.only(TargetPlatform.android), skip: kIsWeb); // [intended] rasterization is not used on the web.

  testWidgets('Setting PageRoute.allowSnapshotting to false overrides ZoomPageTransitionsBuilder.allowSnapshotting = true', (WidgetTester tester) async {
    await tester.pumpWidget(
      boilerplate(
        themeAllowSnapshotting: true,
        secondRouteAllowSnapshotting: false,
      ),
    );

    final Finder page1 = find.text('Page 1');
    final Finder page2 = find.text('Page 2');

    // Transitioning from page 1 to page 2.
    tester.state<NavigatorState>(find.byType(Navigator)).pushNamed('/2');
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 50));

    // First route should be snapshotted.
    expect(isTransitioningWithSnapshotting(tester, page1), isTrue);

    // Second route should not be snapshotted.
    expect(isTransitioningWithSnapshotting(tester, page2), isFalse);

    await tester.pumpAndSettle();
  }, variant: TargetPlatformVariant.only(TargetPlatform.android), skip: kIsWeb); // [intended] rasterization is not used on the web.

  testWidgets('_ZoomPageTransition only causes child widget built once', (WidgetTester tester) async {
    // Regression test for https://github.com/flutter/flutter/issues/58345

    int builtCount = 0;

    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
      '/': (BuildContext context) => Material(
        child: TextButton(
          child: const Text('push'),
          onPressed: () { Navigator.of(context).pushNamed('/b'); },
        ),
      ),
      '/b': (BuildContext context) => StatefulBuilder(
        builder: (BuildContext context, StateSetter setState) {
          builtCount++; // Increase [builtCount] each time the widget build
          return TextButton(
            child: const Text('pop'),
            onPressed: () { Navigator.pop(context); },
          );
        },
      ),
    };

    await tester.pumpWidget(
      MaterialApp(
        theme: ThemeData(
          pageTransitionsTheme: const PageTransitionsTheme(
            builders: <TargetPlatform, PageTransitionsBuilder>{
              TargetPlatform.android: ZoomPageTransitionsBuilder(), // creates a _ZoomPageTransition
            },
          ),
        ),
        routes: routes,
      ),
    );

    // No matter push or pop was called, the child widget should built only once.
    await tester.tap(find.text('push'));
    await tester.pumpAndSettle();
    expect(builtCount, 1);

    await tester.tap(find.text('pop'));
    await tester.pumpAndSettle();
    expect(builtCount, 1);
  }, variant: TargetPlatformVariant.only(TargetPlatform.android));

  testWidgets('predictive back gestures pop the route on all platforms regardless of whether their transition handles predictive back', (WidgetTester tester) async {
    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
      '/': (BuildContext context) => Material(
        child: TextButton(
          child: const Text('push'),
          onPressed: () { Navigator.of(context).pushNamed('/b'); },
        ),
      ),
      '/b': (BuildContext context) => const Text('page b'),
    };

    await tester.pumpWidget(
      MaterialApp(
        routes: routes,
      ),
    );

    expect(find.text('push'), findsOneWidget);
    expect(find.text('page b'), findsNothing);

    await tester.tap(find.text('push'));
    await tester.pumpAndSettle();

    expect(find.text('push'), findsNothing);
    expect(find.text('page b'), findsOneWidget);

    // Start a system pop gesture.
    final ByteData startMessage = const StandardMethodCodec().encodeMethodCall(
      const MethodCall(
        'startBackGesture',
        <String, dynamic>{
          'touchOffset': <double>[5.0, 300.0],
          'progress': 0.0,
          'swipeEdge': 0, // left
        },
      ),
    );
    await binding.defaultBinaryMessenger.handlePlatformMessage(
      'flutter/backgesture',
      startMessage,
      (ByteData? _) {},
    );
    await tester.pump();

    expect(find.text('push'), findsNothing);
    expect(find.text('page b'), findsOneWidget);

    // Drag the system back gesture far enough to commit.
    final ByteData updateMessage = const StandardMethodCodec().encodeMethodCall(
      const MethodCall(
        'updateBackGestureProgress',
        <String, dynamic>{
          'x': 100.0,
          'y': 300.0,
          'progress': 0.35,
          'swipeEdge': 0, // left
        },
      ),
    );
    await binding.defaultBinaryMessenger.handlePlatformMessage(
      'flutter/backgesture',
      updateMessage,
      (ByteData? _) {},
    );
    await tester.pumpAndSettle();

    expect(find.text('push'), findsNothing);
    expect(find.text('page b'), findsOneWidget);

    // Commit the system back gesture.
    final ByteData commitMessage = const StandardMethodCodec().encodeMethodCall(
      const MethodCall(
        'commitBackGesture',
      ),
    );
    await binding.defaultBinaryMessenger.handlePlatformMessage(
      'flutter/backgesture',
      commitMessage,
      (ByteData? _) {},
    );
    await tester.pumpAndSettle();

    expect(find.text('push'), findsOneWidget);
    expect(find.text('page b'), findsNothing);
  }, variant: TargetPlatformVariant.all());

  testWidgets('ZoomPageTransitionsBuilder uses theme color during transition effects', (WidgetTester tester) async {
    // Color that is being tested for presence.
    const Color themeTestSurfaceColor = Color.fromARGB(255, 195, 255, 0);

    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
      '/': (BuildContext context) => Material(
        child: Scaffold(
          appBar: AppBar(
            title: const Text('Home Page'),
          ),
          body: Center(
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                ElevatedButton(
                  onPressed: () {
                    Navigator.pushNamed(context, '/scaffolded');
                  },
                  child: const Text('Route with scaffold!'),
                ),
                ElevatedButton(
                  onPressed: () {
                    Navigator.pushNamed(context, '/not-scaffolded');
                  },
                  child: const Text('Route with NO scaffold!'),
                ),
              ],
            ),
          ),
        ),
      ),
      '/scaffolded': (BuildContext context) => Material(
        child: Scaffold(
          appBar: AppBar(
            title: const Text('Scaffolded Page'),
          ),
          body: Center(
            child: ElevatedButton(
              onPressed: () {
                Navigator.pop(context);
              },
              child: const Text('Back to home route...'),
            ),
          ),
        ),
      ),
      '/not-scaffolded': (BuildContext context) => Material(
        child: Center(
          child: ElevatedButton(
            onPressed: () {
              Navigator.pop(context);
            },
            child: const Text('Back to home route...'),
          ),
        ),
      ),
    };

    await tester.pumpWidget(
      MaterialApp(
        theme: ThemeData(
          colorScheme: ColorScheme.fromSeed(seedColor: Colors.blue, surface: themeTestSurfaceColor),
          pageTransitionsTheme: PageTransitionsTheme(
            builders: <TargetPlatform, PageTransitionsBuilder>{
              // Force all platforms to use ZoomPageTransitionsBuilder to test each one.
              for (final TargetPlatform platform in TargetPlatform.values) platform: const ZoomPageTransitionsBuilder(),
            },
          ),
        ),
        routes: routes,
      ),
    );

    // Go to scaffolded page.
    await tester.tap(find.text('Route with scaffold!'));

    // Pump till animation is half-way through.
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 75));

    // Verify that the render box is painting the right color for scaffolded pages.
    final RenderBox scaffoldedRenderBox = tester.firstRenderObject<RenderBox>(find.byType(MaterialApp));
    // Expect the color to be at exactly 12.2% opacity at this time.
    expect(scaffoldedRenderBox, paints..rect(color: themeTestSurfaceColor.withOpacity(0.122)));

    await tester.pumpAndSettle();

    // Go back home and then go to non-scaffolded page.
    await tester.tap(find.text('Back to home route...'));
    await tester.pumpAndSettle();
    await tester.tap(find.text('Route with NO scaffold!'));

    // Pump till animation is half-way through.
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 125));

    // Verify that the render box is painting the right color for non-scaffolded pages.
    final RenderBox nonScaffoldedRenderBox = tester.firstRenderObject<RenderBox>(find.byType(MaterialApp));
    // Expect the color to be at exactly 59.6% opacity at this time.
    expect(nonScaffoldedRenderBox, paints..rect(color: themeTestSurfaceColor.withOpacity(0.596)));

    await tester.pumpAndSettle();

    // Verify that the transition successfully completed.
    expect(find.text('Back to home route...'), findsOneWidget);
  }, variant: TargetPlatformVariant.all());

  testWidgets('ZoomPageTransitionsBuilder uses developer-provided color during transition effects if provided', (WidgetTester tester) async {
    // Color that is being tested for presence.
    const Color testSurfaceColor = Colors.red;

    final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
      '/': (BuildContext context) => Material(
        child: Scaffold(
          appBar: AppBar(
            title: const Text('Home Page'),
          ),
          body: Center(
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                ElevatedButton(
                  onPressed: () {
                    Navigator.pushNamed(context, '/scaffolded');
                  },
                  child: const Text('Route with scaffold!'),
                ),
                ElevatedButton(
                  onPressed: () {
                    Navigator.pushNamed(context, '/not-scaffolded');
                  },
                  child: const Text('Route with NO scaffold!'),
                ),
              ],
            ),
          ),
        ),
      ),
      '/scaffolded': (BuildContext context) => Material(
        child: Scaffold(
          appBar: AppBar(
            title: const Text('Scaffolded Page'),
          ),
          body: Center(
            child: ElevatedButton(
              onPressed: () {
                Navigator.pop(context);
              },
              child: const Text('Back to home route...'),
            ),
          ),
        ),
      ),
      '/not-scaffolded': (BuildContext context) => Material(
        child: Center(
          child: ElevatedButton(
            onPressed: () {
              Navigator.pop(context);
            },
            child: const Text('Back to home route...'),
          ),
        ),
      ),
    };

    await tester.pumpWidget(
      MaterialApp(
        theme: ThemeData(
          colorScheme: ColorScheme.fromSeed(seedColor: Colors.blue, surface: Colors.blue),
          pageTransitionsTheme: PageTransitionsTheme(
            builders: <TargetPlatform, PageTransitionsBuilder>{
              // Force all platforms to use ZoomPageTransitionsBuilder to test each one.
              for (final TargetPlatform platform in TargetPlatform.values) platform: const ZoomPageTransitionsBuilder(backgroundColor: testSurfaceColor),
            },
          ),
        ),
        routes: routes,
      ),
    );

    // Go to scaffolded page.
    await tester.tap(find.text('Route with scaffold!'));

    // Pump till animation is half-way through.
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 75));

    // Verify that the render box is painting the right color for scaffolded pages.
    final RenderBox scaffoldedRenderBox = tester.firstRenderObject<RenderBox>(find.byType(MaterialApp));
    // Expect the color to be at exactly 12.2% opacity at this time.
    expect(scaffoldedRenderBox, paints..rect(color: testSurfaceColor.withOpacity(0.122)));

    await tester.pumpAndSettle();

    // Go back home and then go to non-scaffolded page.
    await tester.tap(find.text('Back to home route...'));
    await tester.pumpAndSettle();
    await tester.tap(find.text('Route with NO scaffold!'));

    // Pump till animation is half-way through.
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 125));

    // Verify that the render box is painting the right color for non-scaffolded pages.
    final RenderBox nonScaffoldedRenderBox = tester.firstRenderObject<RenderBox>(find.byType(MaterialApp));
    // Expect the color to be at exactly 59.6% opacity at this time.
    expect(nonScaffoldedRenderBox, paints..rect(color: testSurfaceColor.withOpacity(0.596)));

    await tester.pumpAndSettle();

    // Verify that the transition successfully completed.
    expect(find.text('Back to home route...'), findsOneWidget);
  }, variant: TargetPlatformVariant.all());
}