flutter/examples/api/test/material/app/app.0_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/material.dart';
import 'package:flutter_api_samples/material/app/app.0.dart'
    as example;
import 'package:flutter_test/flutter_test.dart';

void main() {
  testWidgets('Theme animation can be customized using AnimationStyle', (WidgetTester tester) async {
    await tester.pumpWidget(
      const example.MaterialAppExample(),
    );

    Material getScaffoldMaterial() {
      return tester.widget<Material>(find.descendant(
        of: find.byType(Scaffold),
        matching: find.byType(Material).first,
      ));
    }

    final ThemeData lightTheme = ThemeData(colorSchemeSeed: Colors.green);
    final ThemeData darkTheme = ThemeData(
      colorSchemeSeed: Colors.green,
      brightness: Brightness.dark,
    );

    // Test the default animation.
    expect(getScaffoldMaterial().color, lightTheme.colorScheme.background);

    await tester.tap(find.text( 'Switch Theme Mode'));
    await tester.pump();
    // Advance the animation by half of the default duration.
    await tester.pump(const Duration(milliseconds: 100));

    // The Scaffold background color is updated.
    expect(
      getScaffoldMaterial().color,
      Color.lerp(lightTheme.colorScheme.background, darkTheme.colorScheme.background, 0.5),
    );

    await tester.pumpAndSettle();

    // The Scaffold background color is now fully dark.
    expect(getScaffoldMaterial().color, darkTheme.colorScheme.background);

    // Test the custom animation curve and duration.
    await tester.tap(find.text('Custom'));
    await tester.pumpAndSettle();

    await tester.tap(find.text('Switch Theme Mode'));
    await tester.pump();
    // Advance the animation by half of the custom duration.
    await tester.pump(const Duration(milliseconds: 500));

    // The Scaffold background color is updated.
    expect(getScaffoldMaterial().color, const Color(0xff3c3e3b));

    await tester.pumpAndSettle();

    // The Scaffold background color is now fully light.
    expect(getScaffoldMaterial().color, lightTheme.colorScheme.background);

    // Test the no animation style.
    await tester.tap(find.text('None'));
    await tester.pumpAndSettle();

    await tester.tap(find.text('Switch Theme Mode'));
    // Advance the animation by only one frame.
    await tester.pump();

    // The Scaffold background color is updated immediately.
    expect(getScaffoldMaterial().color, darkTheme.colorScheme.background);
  });
}