diff --git a/lib/main.dart b/lib/main.dart
index d2c30c8b..4fb4f85d 100644
--- a/lib/main.dart
+++ b/lib/main.dart
@@ -75,7 +75,11 @@ void _initLog() {
 }
 
 Future<void> _initPref() async {
-  await Pref().init();
+  final provider = PrefSharedPreferencesProvider();
+  await provider.init();
+  final pref = Pref.scoped(provider);
+  Pref.setGlobalInstance(pref);
+
   if (Pref().getLastVersion() == null) {
     if (Pref().getSetupProgress() == null) {
       // new install
diff --git a/lib/pref.dart b/lib/pref.dart
index 1c710382..2a2b8780 100644
--- a/lib/pref.dart
+++ b/lib/pref.dart
@@ -9,21 +9,21 @@ import 'package:nc_photos/use_case/compat/v32.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
 class Pref {
-  factory Pref() => _inst;
+  factory Pref() {
+    _inst ??= Pref.scoped(PrefMemoryProvider());
+    return _inst!;
+  }
 
-  Pref.scoped();
+  Pref.scoped(this.provider);
 
-  Future<void> init() async {
-    if (await CompatV32.isPrefNeedMigration()) {
-      await CompatV32.migratePref();
-    }
-    return SharedPreferences.getInstance().then((pref) {
-      _pref = pref;
-    });
+  /// Set the global [Pref] instance returned by the default constructor
+  static void setGlobalInstance(Pref pref) {
+    assert(_inst == null);
+    _inst = pref;
   }
 
   List<PrefAccount>? getAccounts2() {
-    final jsonObjs = _pref.getStringList(_toKey(PrefKey.accounts2));
+    final jsonObjs = provider.getStringList(PrefKey.accounts2);
     return jsonObjs?.map((e) => PrefAccount.fromJson(jsonDecode(e))).toList();
   }
 
@@ -31,127 +31,129 @@ class Pref {
       getAccounts2() ?? def;
   Future<bool> setAccounts2(List<PrefAccount> value) {
     final jsons = value.map((e) => jsonEncode(e.toJson())).toList();
-    return _setStringList(PrefKey.accounts2, jsons);
+    return provider.setStringList(PrefKey.accounts2, jsons);
   }
 
-  int? getCurrentAccountIndex() =>
-      _pref.getInt(_toKey(PrefKey.currentAccountIndex));
+  int? getCurrentAccountIndex() => provider.getInt(PrefKey.currentAccountIndex);
   int getCurrentAccountIndexOr(int def) => getCurrentAccountIndex() ?? def;
   Future<bool> setCurrentAccountIndex(int value) =>
-      _setInt(PrefKey.currentAccountIndex, value);
+      provider.setInt(PrefKey.currentAccountIndex, value);
 
-  int? getHomePhotosZoomLevel() =>
-      _pref.getInt(_toKey(PrefKey.homePhotosZoomLevel));
+  int? getHomePhotosZoomLevel() => provider.getInt(PrefKey.homePhotosZoomLevel);
   int getHomePhotosZoomLevelOr(int def) => getHomePhotosZoomLevel() ?? def;
   Future<bool> setHomePhotosZoomLevel(int value) =>
-      _setInt(PrefKey.homePhotosZoomLevel, value);
+      provider.setInt(PrefKey.homePhotosZoomLevel, value);
 
   int? getAlbumBrowserZoomLevel() =>
-      _pref.getInt(_toKey(PrefKey.albumBrowserZoomLevel));
+      provider.getInt(PrefKey.albumBrowserZoomLevel);
   int getAlbumBrowserZoomLevelOr(int def) => getAlbumBrowserZoomLevel() ?? def;
   Future<bool> setAlbumBrowserZoomLevel(int value) =>
-      _setInt(PrefKey.albumBrowserZoomLevel, value);
+      provider.setInt(PrefKey.albumBrowserZoomLevel, value);
 
-  int? getHomeAlbumsSort() => _pref.getInt(_toKey(PrefKey.homeAlbumsSort));
+  int? getHomeAlbumsSort() => provider.getInt(PrefKey.homeAlbumsSort);
   int getHomeAlbumsSortOr(int def) => getHomeAlbumsSort() ?? def;
   Future<bool> setHomeAlbumsSort(int value) =>
-      _setInt(PrefKey.homeAlbumsSort, value);
+      provider.setInt(PrefKey.homeAlbumsSort, value);
 
-  bool? isEnableExif() => _pref.getBool(_toKey(PrefKey.enableExif));
+  bool? isEnableExif() => provider.getBool(PrefKey.enableExif);
   bool isEnableExifOr([bool def = true]) => isEnableExif() ?? def;
-  Future<bool> setEnableExif(bool value) => _setBool(PrefKey.enableExif, value);
+  Future<bool> setEnableExif(bool value) =>
+      provider.setBool(PrefKey.enableExif, value);
 
   int? getViewerScreenBrightness() =>
-      _pref.getInt(_toKey(PrefKey.viewerScreenBrightness));
+      provider.getInt(PrefKey.viewerScreenBrightness);
   int getViewerScreenBrightnessOr([int def = -1]) =>
       getViewerScreenBrightness() ?? def;
   Future<bool> setViewerScreenBrightness(int value) =>
-      _setInt(PrefKey.viewerScreenBrightness, value);
+      provider.setInt(PrefKey.viewerScreenBrightness, value);
 
   bool? isViewerForceRotation() =>
-      _pref.getBool(_toKey(PrefKey.viewerForceRotation));
+      provider.getBool(PrefKey.viewerForceRotation);
   bool isViewerForceRotationOr([bool def = false]) =>
       isViewerForceRotation() ?? def;
   Future<bool> setViewerForceRotation(bool value) =>
-      _setBool(PrefKey.viewerForceRotation, value);
+      provider.setBool(PrefKey.viewerForceRotation, value);
 
-  int? getSetupProgress() => _pref.getInt(_toKey(PrefKey.setupProgress));
+  int? getSetupProgress() => provider.getInt(PrefKey.setupProgress);
   int getSetupProgressOr([int def = 0]) => getSetupProgress() ?? def;
   Future<bool> setSetupProgress(int value) =>
-      _setInt(PrefKey.setupProgress, value);
+      provider.setInt(PrefKey.setupProgress, value);
 
   /// Return the version number when the app last ran
-  int? getLastVersion() => _pref.getInt(_toKey(PrefKey.lastVersion));
+  int? getLastVersion() => provider.getInt(PrefKey.lastVersion);
   int getLastVersionOr(int def) => getLastVersion() ?? def;
-  Future<bool> setLastVersion(int value) => _setInt(PrefKey.lastVersion, value);
+  Future<bool> setLastVersion(int value) =>
+      provider.setInt(PrefKey.lastVersion, value);
 
-  bool? isDarkTheme() => _pref.getBool(_toKey(PrefKey.darkTheme));
+  bool? isDarkTheme() => provider.getBool(PrefKey.darkTheme);
   bool isDarkThemeOr(bool def) => isDarkTheme() ?? def;
-  Future<bool> setDarkTheme(bool value) => _setBool(PrefKey.darkTheme, value);
+  Future<bool> setDarkTheme(bool value) =>
+      provider.setBool(PrefKey.darkTheme, value);
 
-  bool? isFollowSystemTheme() =>
-      _pref.getBool(_toKey(PrefKey.followSystemTheme));
+  bool? isFollowSystemTheme() => provider.getBool(PrefKey.followSystemTheme);
   bool isFollowSystemThemeOr(bool def) => isFollowSystemTheme() ?? def;
   Future<bool> setFollowSystemTheme(bool value) =>
-      _setBool(PrefKey.followSystemTheme, value);
+      provider.setBool(PrefKey.followSystemTheme, value);
 
   bool? isUseBlackInDarkTheme() =>
-      _pref.getBool(_toKey(PrefKey.useBlackInDarkTheme));
+      provider.getBool(PrefKey.useBlackInDarkTheme);
   bool isUseBlackInDarkThemeOr(bool def) => isUseBlackInDarkTheme() ?? def;
   Future<bool> setUseBlackInDarkTheme(bool value) =>
-      _setBool(PrefKey.useBlackInDarkTheme, value);
+      provider.setBool(PrefKey.useBlackInDarkTheme, value);
 
-  int? getLanguage() => _pref.getInt(_toKey(PrefKey.language));
+  int? getLanguage() => provider.getInt(PrefKey.language);
   int getLanguageOr(int def) => getLanguage() ?? def;
-  Future<bool> setLanguage(int value) => _setInt(PrefKey.language, value);
+  Future<bool> setLanguage(int value) =>
+      provider.setInt(PrefKey.language, value);
 
-  int? getSlideshowDuration() =>
-      _pref.getInt(_toKey(PrefKey.slideshowDuration));
+  int? getSlideshowDuration() => provider.getInt(PrefKey.slideshowDuration);
   int getSlideshowDurationOr(int def) => getSlideshowDuration() ?? def;
   Future<bool> setSlideshowDuration(int value) =>
-      _setInt(PrefKey.slideshowDuration, value);
+      provider.setInt(PrefKey.slideshowDuration, value);
 
-  bool? isSlideshowShuffle() =>
-      _pref.getBool(_toKey(PrefKey.isSlideshowShuffle));
+  bool? isSlideshowShuffle() => provider.getBool(PrefKey.isSlideshowShuffle);
   bool isSlideshowShuffleOr(bool def) => isSlideshowShuffle() ?? def;
   Future<bool> setSlideshowShuffle(bool value) =>
-      _setBool(PrefKey.isSlideshowShuffle, value);
+      provider.setBool(PrefKey.isSlideshowShuffle, value);
 
-  bool? isSlideshowRepeat() => _pref.getBool(_toKey(PrefKey.isSlideshowRepeat));
+  bool? isSlideshowRepeat() => provider.getBool(PrefKey.isSlideshowRepeat);
   bool isSlideshowRepeatOr(bool def) => isSlideshowRepeat() ?? def;
   Future<bool> setSlideshowRepeat(bool value) =>
-      _setBool(PrefKey.isSlideshowRepeat, value);
+      provider.setBool(PrefKey.isSlideshowRepeat, value);
 
   bool? isAlbumBrowserShowDate() =>
-      _pref.getBool(_toKey(PrefKey.isAlbumBrowserShowDate));
+      provider.getBool(PrefKey.isAlbumBrowserShowDate);
   bool isAlbumBrowserShowDateOr([bool def = false]) =>
       isAlbumBrowserShowDate() ?? def;
   Future<bool> setAlbumBrowserShowDate(bool value) =>
-      _setBool(PrefKey.isAlbumBrowserShowDate, value);
+      provider.setBool(PrefKey.isAlbumBrowserShowDate, value);
 
-  bool? hasNewSharedAlbum() => _pref.getBool(_toKey(PrefKey.newSharedAlbum));
+  bool? hasNewSharedAlbum() => provider.getBool(PrefKey.newSharedAlbum);
   bool hasNewSharedAlbumOr(bool def) => hasNewSharedAlbum() ?? def;
   Future<bool> setNewSharedAlbum(bool value) =>
-      _setBool(PrefKey.newSharedAlbum, value);
+      provider.setBool(PrefKey.newSharedAlbum, value);
 
   bool? isLabEnableSharedAlbum() =>
-      _pref.getBool(_toKey(PrefKey.labEnableSharedAlbum));
+      provider.getBool(PrefKey.labEnableSharedAlbum);
   bool isLabEnableSharedAlbumOr(bool def) => isLabEnableSharedAlbum() ?? def;
   Future<bool> setLabEnableSharedAlbum(bool value) =>
-      _setBool(PrefKey.labEnableSharedAlbum, value);
+      provider.setBool(PrefKey.labEnableSharedAlbum, value);
 
-  Future<bool> _setBool(PrefKey key, bool value) async {
-    return _onPostSet(await _pref.setBool(_toKey(key), value), key, value);
-  }
+  final PrefProvider provider;
 
-  Future<bool> _setInt(PrefKey key, int value) async {
-    return _onPostSet(await _pref.setInt(_toKey(key), value), key, value);
-  }
+  static Pref? _inst;
+}
 
-  Future<bool> _setStringList(PrefKey key, List<String> value) async {
-    return _onPostSet(
-        await _pref.setStringList(_toKey(key), value), key, value);
-  }
+/// Provide the data for [Pref]
+abstract class PrefProvider {
+  bool? getBool(PrefKey key);
+  Future<bool> setBool(PrefKey key, bool value);
+
+  int? getInt(PrefKey key);
+  Future<bool> setInt(PrefKey key, int value);
+
+  List<String>? getStringList(PrefKey key);
+  Future<bool> setStringList(PrefKey key, List<String> value);
 
   bool _onPostSet(bool result, PrefKey key, dynamic value) {
     if (result) {
@@ -161,56 +163,90 @@ class Pref {
       return false;
     }
   }
+}
 
-  String _toKey(PrefKey key) {
-    switch (key) {
-      case PrefKey.accounts2:
-        return "accounts2";
-      case PrefKey.currentAccountIndex:
-        return "currentAccountIndex";
-      case PrefKey.homePhotosZoomLevel:
-        return "homePhotosZoomLevel";
-      case PrefKey.albumBrowserZoomLevel:
-        return "albumViewerZoomLevel";
-      case PrefKey.homeAlbumsSort:
-        return "homeAlbumsSort";
-      case PrefKey.enableExif:
-        return "isEnableExif";
-      case PrefKey.viewerScreenBrightness:
-        return "viewerScreenBrightness";
-      case PrefKey.viewerForceRotation:
-        return "viewerForceRotation";
-      case PrefKey.setupProgress:
-        return "setupProgress";
-      case PrefKey.lastVersion:
-        return "lastVersion";
-      case PrefKey.darkTheme:
-        return "isDarkTheme";
-      case PrefKey.followSystemTheme:
-        return "isFollowSystemTheme";
-      case PrefKey.useBlackInDarkTheme:
-        return "isUseBlackInDarkTheme";
-      case PrefKey.language:
-        return "language";
-      case PrefKey.newSharedAlbum:
-        return "hasNewSharedAlbum";
-      case PrefKey.labEnableSharedAlbum:
-        return "isLabEnableSharedAlbum";
-      case PrefKey.slideshowDuration:
-        return "slideshowDuration";
-      case PrefKey.isSlideshowShuffle:
-        return "isSlideshowShuffle";
-      case PrefKey.isSlideshowRepeat:
-        return "isSlideshowRepeat";
-      case PrefKey.isAlbumBrowserShowDate:
-        return "isAlbumBrowserShowDate";
+/// [Pref] stored with [SharedPreferences] lib
+class PrefSharedPreferencesProvider extends PrefProvider {
+  Future<void> init() async {
+    if (await CompatV32.isPrefNeedMigration()) {
+      await CompatV32.migratePref();
     }
+    return SharedPreferences.getInstance().then((pref) {
+      _pref = pref;
+    });
+  }
+
+  @override
+  getBool(PrefKey key) => _pref.getBool(key.toStringKey());
+
+  @override
+  setBool(PrefKey key, bool value) async {
+    return _onPostSet(
+        await _pref.setBool(key.toStringKey(), value), key, value);
+  }
+
+  @override
+  getInt(PrefKey key) => _pref.getInt(key.toStringKey());
+
+  @override
+  setInt(PrefKey key, int value) async {
+    return _onPostSet(await _pref.setInt(key.toStringKey(), value), key, value);
+  }
+
+  @override
+  getStringList(PrefKey key) => _pref.getStringList(key.toStringKey());
+
+  @override
+  setStringList(PrefKey key, List<String> value) async {
+    return _onPostSet(
+        await _pref.setStringList(key.toStringKey(), value), key, value);
   }
 
-  static late final _inst = Pref.scoped();
   late SharedPreferences _pref;
 }
 
+/// [Pref] stored in memory
+class PrefMemoryProvider extends PrefProvider {
+  PrefMemoryProvider([
+    Map<String, dynamic> initialData = const <String, dynamic>{},
+  ]) : _data = Map.of(initialData);
+
+  @override
+  getBool(PrefKey key) => _data[key.toStringKey()];
+
+  @override
+  setBool(PrefKey key, bool value) async {
+    return _onPostSet(() {
+      _data[key.toStringKey()] = value;
+      return true;
+    }(), key, value);
+  }
+
+  @override
+  getInt(PrefKey key) => _data[key.toStringKey()];
+
+  @override
+  setInt(PrefKey key, int value) async {
+    return _onPostSet(() {
+      _data[key.toStringKey()] = value;
+      return true;
+    }(), key, value);
+  }
+
+  @override
+  getStringList(PrefKey key) => _data[key.toStringKey()];
+
+  @override
+  setStringList(PrefKey key, List<String> value) async {
+    return _onPostSet(() {
+      _data[key.toStringKey()] = value;
+      return true;
+    }(), key, value);
+  }
+
+  final Map<String, dynamic> _data;
+}
+
 class PrefAccount {
   const PrefAccount(
     this.account, [
@@ -274,6 +310,53 @@ enum PrefKey {
   isAlbumBrowserShowDate,
 }
 
+extension on PrefKey {
+  String toStringKey() {
+    switch (this) {
+      case PrefKey.accounts2:
+        return "accounts2";
+      case PrefKey.currentAccountIndex:
+        return "currentAccountIndex";
+      case PrefKey.homePhotosZoomLevel:
+        return "homePhotosZoomLevel";
+      case PrefKey.albumBrowserZoomLevel:
+        return "albumViewerZoomLevel";
+      case PrefKey.homeAlbumsSort:
+        return "homeAlbumsSort";
+      case PrefKey.enableExif:
+        return "isEnableExif";
+      case PrefKey.viewerScreenBrightness:
+        return "viewerScreenBrightness";
+      case PrefKey.viewerForceRotation:
+        return "viewerForceRotation";
+      case PrefKey.setupProgress:
+        return "setupProgress";
+      case PrefKey.lastVersion:
+        return "lastVersion";
+      case PrefKey.darkTheme:
+        return "isDarkTheme";
+      case PrefKey.followSystemTheme:
+        return "isFollowSystemTheme";
+      case PrefKey.useBlackInDarkTheme:
+        return "isUseBlackInDarkTheme";
+      case PrefKey.language:
+        return "language";
+      case PrefKey.newSharedAlbum:
+        return "hasNewSharedAlbum";
+      case PrefKey.labEnableSharedAlbum:
+        return "isLabEnableSharedAlbum";
+      case PrefKey.slideshowDuration:
+        return "slideshowDuration";
+      case PrefKey.isSlideshowShuffle:
+        return "isSlideshowShuffle";
+      case PrefKey.isSlideshowRepeat:
+        return "isSlideshowRepeat";
+      case PrefKey.isAlbumBrowserShowDate:
+        return "isAlbumBrowserShowDate";
+    }
+  }
+}
+
 extension PrefExtension on Pref {
   Account? getCurrentAccount() {
     try {