在 flutter 上测试 shared_preferences

Question

我正在编写一个 flutter 应用程序，并且在编写测试时遇到了这个问题。此方法应该将数据写入 TextFields 并点击一个将这些数据保存在 SharedPrefs 中的按钮:

testWidgets('Click on login saves the credentials',
      (WidgetTester tester) async {

    await tester.pumpWidget(MyApp());

    await tester.enterText(find.byKey(Key('phoneInput')), 'test');
    await tester.enterText(find.byKey(Key('passwordInput')), 'test');
    await tester.tap(find.byIcon(Icons.lock));

    SharedPreferences prefs = await SharedPreferences.getInstance();
    expect(prefs.getString('phone'), 'test');
    expect(prefs.getString('password'), 'test');
  });

此测试将无法获取 SharedPreferences 实例并出现此错误:

The following TimeoutException was thrown running a test:
TimeoutException after 0:00:03.500000: The test exceeded the timeout. It may have hung.
Consider using "addTime" to increase the timeout before expensive operations.

更新:似乎问题实际上不是超时，因为即使有 60 秒，测试也无法解析 SharedPreferences 实例。

Answer 1

您需要从 shared_preferences 模拟 getAll(引用:https://pub.dartlang.org/packages/shared_preferences)

示例代码如下:

import 'package:shared_preferences/shared_preferences.dart';
import 'package:flutter/services.dart'; // <-- needed for `MethodChannel`

void main() {

  setUpAll(() {
    const MethodChannel('plugins.flutter.io/shared_preferences')
        .setMockMethodCallHandler((MethodCall methodCall) async {
      if (methodCall.method == 'getAll') {
        return <String, dynamic>{}; // set initial values here if desired
      }
      return null;
    });
  });

  testWidgets('Click on login saves the credentials',
      (WidgetTester tester) async {
    await tester.pumpWidget(MyApp());

    await tester.enterText(find.byKey(Key('phoneInput')), 'test');
    await tester.enterText(find.byKey(Key('passwordInput')), 'test');
    await tester.tap(find.byIcon(Icons.lock));

    SharedPreferences prefs = await SharedPreferences.getInstance();
    expect(prefs.getString('phone'), 'test');
    expect(prefs.getString('password'), 'test');
  });
}

---

原答案:

testWidgets('Click on login saves the credentials',
      (WidgetTester tester) async {
      final AutomatedTestWidgetsFlutterBinding binding = tester.binding;
      binding.addTime(const Duration(seconds: 10)); // or longer if needed
    await tester.pumpWidget(MyApp());

    await tester.enterText(find.byKey(Key('phoneInput')), 'test');
    await tester.enterText(find.byKey(Key('passwordInput')), 'test');
    await tester.tap(find.byIcon(Icons.lock));

    SharedPreferences prefs = await SharedPreferences.getInstance();
    expect(prefs.getString('phone'), 'test');
    expect(prefs.getString('password'), 'test');
  });