Flutter: 'package:shared_preferences/shared_preferences.dart': Неудачное утверждение: строка 33 поз. 16: 'key.startsWith(_prefix)': неверно

Я запускаю некоторые модульные тесты для общих настроек. Я делал вспомогательный класс, чтобы нам не приходилось писать один и тот же код снова и снова.

Что бы я ни пробовал, я всегда получаю одну и ту же ошибку снова и снова. Вы найдете класс, который я тестирую, тестовый класс и трассировку стека.

Я надеюсь, что это что-то глупое, что я забыл. Я пробовал эти ресурсы:

• https://pub.dartlang.org/packages/shared_preferences
• модульное тестирование флаттер
• https://flutter.dev/docs/cookbook/persistence/ключ-значение

shared_preferences_helper_test.dart:

import 'package:flutter/services.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:shoppaworld_client_app/shared_preferences_helper.dart';

// at the moment testing
void main() {

  SharedPreferencesHelper sharedPreferencesHelper;

  setUpAll(() {
    sharedPreferencesHelper = SharedPreferencesHelper();

    const MethodChannel('plugins.flutter.io/shared_preferences')
        .setMockMethodCallHandler((MethodCall methodCall) async {
      if (methodCall.method == 'getAll') {
        return <String, dynamic> {
          'test-string' : 'string-value',
          'test-int' : 420,
          'test-bool' : true
        }; // set initial values here if desired
      }
      return null;
    });

  });

  test('test if the testing works', () async {

    SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
    sharedPreferences.setString('test-string-infunction', 'wow');
    var value = sharedPreferences.getString('test-string-infunction');


    print(value);
    expect(value, 'wow');

  });

  group('unit test 1: read shared preferences', () {

    test('shared preferences string', () async {

      String value = await sharedPreferencesHelper.readValueFromKey("test-string");

      print(value);
      expect(value, 'string-value');

    });
    test('shared preferences empty', () async {

      var value = await sharedPreferencesHelper.readValueFromKey("does_not_exist");

      expect(value, null);

    });

  });


  group('unit test 2: write shared preferences', () {
    test('shared preferences string', () async {
      var originalValue = 'test';
      var value = await sharedPreferencesHelper.writeValueToKey("test-string", valueString: originalValue);

      SharedPreferences sharedPreferences = await SharedPreferences.getInstance();


      expect(sharedPreferences.getString('test-string'), originalValue);

    });
    test('shared preferences int', () async {

      var originalValue = 420;
      var value = await sharedPreferencesHelper.writeValueToKey("test-int", valueInt: originalValue);

      SharedPreferences sharedPreferences = await SharedPreferences.getInstance();

      expect(sharedPreferences.getInt('test-int'), originalValue);

    });

    test('shared preferences bool', () async {
      var originalValue = true;
      var value = await sharedPreferencesHelper.writeValueToKey("test-bool", valueBool: originalValue);
      SharedPreferences sharedPreferences = await SharedPreferences.getInstance();

      expect(sharedPreferences.getBool('test-bool'), originalValue);

    });
  });
}

shared_preferences_helper.dart:

import 'dart:async';

import 'package:shared_preferences/shared_preferences.dart';



// this class is meant to relieve developers from boilerplate code
class SharedPreferencesHelper {

  Future<dynamic> readValueFromKey(String key) async {
    SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
    return sharedPreferences.get(key) ?? null;
  }

  writeValueToKey(String key, {String valueString, bool valueBool, int valueInt}) async {
    SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
    if (valueString != null){
      sharedPreferences.setString(key, valueString);
    }
    if (valueBool != null) {
      sharedPreferences.setBool(key, valueBool);
    }
    if (valueInt != null) {
      sharedPreferences.setInt(key, valueInt);
    }
  }

}

трассировки стека:

Testing started at 12:10 ...
/home/geordy/SoftwareDevelopment/flutter/flutter_linux_v1.2.1-stable/flutter/bin/flutter --no-color test --machine test/shared_preferences_helper_test.dart
dart:core                                                 _AssertionError._throwNew
package:shared_preferences/shared_preferences.dart 33:16  SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                _AsyncAwaitCompleter.completeError
package:shared_preferences/shared_preferences.dart        SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                _asyncThenWrapperHelper
package:shared_preferences/shared_preferences.dart        SharedPreferences.getInstance
test/shared_preferences_helper_test.dart 30:67            main.<fn>

'package:shared_preferences/shared_preferences.dart': Failed assertion: line 33 pos 16: 'key.startsWith(_prefix)': is not true.

dart:core                                                            _AssertionError._throwNew
package:shared_preferences/shared_preferences.dart 33:16             SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                           _AsyncAwaitCompleter.completeError
package:shared_preferences/shared_preferences.dart                   SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                           _asyncThenWrapperHelper
package:shared_preferences/shared_preferences.dart                   SharedPreferences.getInstance
package:shoppaworld_client_app/shared_preferences_helper.dart 20:67  SharedPreferencesHelper.readValueFromKey

'package:shared_preferences/shared_preferences.dart': Failed assertion: line 33 pos 16: 'key.startsWith(_prefix)': is not true.

dart:core                                                            _AssertionError._throwNew
package:shared_preferences/shared_preferences.dart 33:16             SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                           _AsyncAwaitCompleter.completeError
package:shared_preferences/shared_preferences.dart                   SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                           _asyncThenWrapperHelper
package:shared_preferences/shared_preferences.dart                   SharedPreferences.getInstance
package:shoppaworld_client_app/shared_preferences_helper.dart 20:67  SharedPreferencesHelper.readValueFromKey

'package:shared_preferences/shared_preferences.dart': Failed assertion: line 33 pos 16: 'key.startsWith(_prefix)': is not true.

dart:core                                                            _AssertionError._throwNew
package:shared_preferences/shared_preferences.dart 33:16             SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                           _AsyncAwaitCompleter.completeError
package:shared_preferences/shared_preferences.dart                   SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                           _asyncThenWrapperHelper
package:shared_preferences/shared_preferences.dart                   SharedPreferences.getInstance
package:shoppaworld_client_app/shared_preferences_helper.dart 25:67  SharedPreferencesHelper.writeValueToKey

'package:shared_preferences/shared_preferences.dart': Failed assertion: line 33 pos 16: 'key.startsWith(_prefix)': is not true.

dart:core                                                            _AssertionError._throwNew
package:shared_preferences/shared_preferences.dart 33:16             SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                           _AsyncAwaitCompleter.completeError
package:shared_preferences/shared_preferences.dart                   SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                           _asyncThenWrapperHelper
package:shared_preferences/shared_preferences.dart                   SharedPreferences.getInstance
package:shoppaworld_client_app/shared_preferences_helper.dart 25:67  SharedPreferencesHelper.writeValueToKey

'package:shared_preferences/shared_preferences.dart': Failed assertion: line 33 pos 16: 'key.startsWith(_prefix)': is not true.

dart:core                                                            _AssertionError._throwNew
package:shared_preferences/shared_preferences.dart 33:16             SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                           _AsyncAwaitCompleter.completeError
package:shared_preferences/shared_preferences.dart                   SharedPreferences.getInstance
===== asynchronous gap ===========================
dart:async                                                           _asyncThenWrapperHelper
package:shared_preferences/shared_preferences.dart                   SharedPreferences.getInstance
package:shoppaworld_client_app/shared_preferences_helper.dart 25:67  SharedPreferencesHelper.writeValueToKey

'package:shared_preferences/shared_preferences.dart': Failed assertion: line 33 pos 16: 'key.startsWith(_prefix)': is not true.