refactor(core): consolidate shared app foundations

test/services/data_aggregation_bridge_test.dart

@@ -20,14 +20,10 @@ import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/plex_client.dart';
 import 'package:plezy/services/settings_service.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
 import '../test_helpers/prefs.dart';
 
-JellyfinConnection _conn() => JellyfinConnection(
-  id: 'srv-1/user-1',
-  baseUrl: 'https://jf.example.com',
-  serverName: 'Home',
-  serverMachineId: 'srv-1',
-  userId: 'user-1',
+JellyfinConnection _conn() => testJellyfinConnection(
   userName: 'edde',
   accessToken: 'tok-abc',
   deviceId: 'dev-xyz',

test/services/download_artwork_service_test.dart

@@ -17,46 +17,10 @@ import 'package:plezy/services/download_artwork_service.dart';
 import 'package:plezy/services/download_storage_service.dart';
 import 'package:plezy/services/settings_service.dart';
 import 'package:plezy/utils/media_server_http_client.dart';
-import 'package:plugin_platform_interface/plugin_platform_interface.dart';
 
+import '../test_helpers/io_fakes.dart';
 import '../test_helpers/prefs.dart';
 
-class _FakePathProvider extends PathProviderPlatform with MockPlatformInterfaceMixin {
-  _FakePathProvider(this.root);
-
-  final Directory root;
-
-  @override
-  Future<String?> getApplicationDocumentsPath() async => _ensure('documents');
-
-  @override
-  Future<String?> getApplicationSupportPath() async => _ensure('support');
-
-  @override
-  Future<String?> getApplicationCachePath() async => _ensure('cache');
-
-  @override
-  Future<String?> getTemporaryPath() async => _ensure('temp');
-
-  String _ensure(String name) {
-    final path = p.join(root.path, name);
-    Directory(path).createSync(recursive: true);
-    return path;
-  }
-}
-
-class _FakeHttpClient extends http.BaseClient {
-  _FakeHttpClient(this.statusCode, this.body);
-
-  final int statusCode;
-  final List<int> body;
-
-  @override
-  Future<http.StreamedResponse> send(http.BaseRequest request) async {
-    return http.StreamedResponse(Stream<List<int>>.value(body), statusCode, request: request);
-  }
-}
-
 class _DelayedCountingHttpClient extends http.BaseClient {
   _DelayedCountingHttpClient(this.body);
 
@@ -80,7 +44,7 @@ void main() {
     SettingsService.resetForTesting();
     DownloadStorageService.resetForTesting();
     tmpRoot = await Directory.systemTemp.createTemp('download_artwork_service_test_');
-    PathProviderPlatform.instance = _FakePathProvider(tmpRoot);
+    PathProviderPlatform.instance = FakePathProvider(tmpRoot);
   });
 
   tearDown(() async {
@@ -114,7 +78,7 @@ void main() {
     await storage.initialize(settings);
     final service = DownloadArtworkService(
       storageService: storage,
-      http: MediaServerHttpClient(client: _FakeHttpClient(200, utf8.encode('image'))),
+      http: MediaServerHttpClient(client: FakeHttpClient(200, utf8.encode('image'))),
     );
 
     const tokenized = 'https://jf/Items/1/Images/Logo?tag=abc&api_key=secret';
@@ -125,7 +89,7 @@ void main() {
 
   test('downloadFile rejects non-success responses without leaving final files', () async {
     final file = File(p.join(tmpRoot.path, 'art.jpg'));
-    final httpClient = MediaServerHttpClient(client: _FakeHttpClient(404, utf8.encode('not found')));
+    final httpClient = MediaServerHttpClient(client: FakeHttpClient(404, utf8.encode('not found')));
 
     await expectLater(
       httpClient.downloadFile('https://example.test/art.jpg', file.path),
@@ -143,7 +107,7 @@ void main() {
     final body = utf8.encode('valid image bytes');
     final service = DownloadArtworkService(
       storageService: storage,
-      http: MediaServerHttpClient(client: _FakeHttpClient(200, body)),
+      http: MediaServerHttpClient(client: FakeHttpClient(200, body)),
     );
 
     const rawPath = 'https://jf/Items/1/Images/Logo?tag=abc&api_key=secret';

test/services/download_manager_service_test.dart

@@ -6,7 +6,6 @@ import 'package:background_downloader/background_downloader.dart';
 import 'package:drift/drift.dart' show Value;
 import 'package:drift/native.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:http/http.dart' as http;
 import 'package:path/path.dart' as p;
 import 'package:path_provider_platform_interface/path_provider_platform_interface.dart';
 import 'package:plezy/database/app_database.dart';
@@ -26,9 +25,9 @@ import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/saf_storage_service.dart';
 import 'package:plezy/services/settings_service.dart';
 import 'package:plezy/utils/media_server_http_client.dart';
-import 'package:plugin_platform_interface/plugin_platform_interface.dart';
 import 'package:saf_util/saf_util_platform_interface.dart';
 
+import '../test_helpers/io_fakes.dart';
 import '../test_helpers/prefs.dart';
 
 void main() {
@@ -190,7 +189,7 @@ void main() {
       SettingsService.resetForTesting();
       DownloadStorageService.resetForTesting();
       final tmpRoot = await Directory.systemTemp.createTemp('download_manager_artwork_repair_test_');
-      PathProviderPlatform.instance = _FakePathProvider(tmpRoot);
+      PathProviderPlatform.instance = FakePathProvider(tmpRoot);
       addTearDown(() async {
         DownloadStorageService.resetForTesting();
         SettingsService.resetForTesting();
@@ -263,7 +262,7 @@ void main() {
         database: db,
         storageService: storage,
         clientResolver: (serverId, {clientScopeId}) => client,
-        http: MediaServerHttpClient(client: _FakeHttpClient(200, utf8.encode('image bytes'))),
+        http: MediaServerHttpClient(client: FakeHttpClient(200, utf8.encode('image bytes'))),
       );
 
       await manager.repairMissingArtworkForDownloads();
@@ -284,7 +283,7 @@ void main() {
       SettingsService.resetForTesting();
       DownloadStorageService.resetForTesting();
       final tmpRoot = await Directory.systemTemp.createTemp('download_manager_delete_test_');
-      PathProviderPlatform.instance = _FakePathProvider(tmpRoot);
+      PathProviderPlatform.instance = FakePathProvider(tmpRoot);
       addTearDown(() async {
         DownloadStorageService.resetForTesting();
         SettingsService.resetForTesting();
@@ -551,7 +550,7 @@ Future<_DeletionResult> _runEpisodeDeletion({required bool saf, bool failVideoDe
   SettingsService.resetForTesting();
   DownloadStorageService.resetForTesting();
   final tmpRoot = await Directory.systemTemp.createTemp('download_manager_backend_delete_test_');
-  PathProviderPlatform.instance = _FakePathProvider(tmpRoot);
+  PathProviderPlatform.instance = FakePathProvider(tmpRoot);
 
   final storage = saf ? DownloadStorageService.forTestingSaf('content://downloads') : DownloadStorageService.instance;
   if (!saf) {
@@ -664,7 +663,7 @@ Future<_ContainerDeletionResult> _runContainerDeletion({required MediaKind kind,
   SettingsService.resetForTesting();
   DownloadStorageService.resetForTesting();
   final tmpRoot = await Directory.systemTemp.createTemp('download_manager_container_delete_test_');
-  PathProviderPlatform.instance = _FakePathProvider(tmpRoot);
+  PathProviderPlatform.instance = FakePathProvider(tmpRoot);
 
   final storage = saf ? DownloadStorageService.forTestingSaf('content://downloads') : DownloadStorageService.instance;
   if (!saf) await storage.initialize(await SettingsService.getInstance());
@@ -939,42 +938,6 @@ class _ScopedJellyfinClient implements MediaServerClient, ScopedMediaServerClien
   dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }
 
-class _FakePathProvider extends PathProviderPlatform with MockPlatformInterfaceMixin {
-  _FakePathProvider(this.root);
-
-  final Directory root;
-
-  @override
-  Future<String?> getApplicationDocumentsPath() async => _ensure('documents');
-
-  @override
-  Future<String?> getApplicationSupportPath() async => _ensure('support');
-
-  @override
-  Future<String?> getApplicationCachePath() async => _ensure('cache');
-
-  @override
-  Future<String?> getTemporaryPath() async => _ensure('temp');
-
-  String _ensure(String name) {
-    final path = p.join(root.path, name);
-    Directory(path).createSync(recursive: true);
-    return path;
-  }
-}
-
-class _FakeHttpClient extends http.BaseClient {
-  _FakeHttpClient(this.statusCode, this.body);
-
-  final int statusCode;
-  final List<int> body;
-
-  @override
-  Future<http.StreamedResponse> send(http.BaseRequest request) async {
-    return http.StreamedResponse(Stream<List<int>>.value(body), statusCode, request: request);
-  }
-}
-
 class _ArtworkRepairClient implements MediaServerClient {
   _ArtworkRepairClient({required this.serverId, required this.items});
 

test/services/download_storage_service_test.dart

@@ -9,42 +9,10 @@ import 'package:plezy/media/media_item.dart';
 import 'package:plezy/media/media_kind.dart';
 import 'package:plezy/services/download_storage_service.dart';
 import 'package:plezy/services/settings_service.dart';
-import 'package:plugin_platform_interface/plugin_platform_interface.dart';
 
+import '../test_helpers/io_fakes.dart';
 import '../test_helpers/prefs.dart';
 
-/// In-test fake PathProviderPlatform that points all directories at a real
-/// on-disk temp folder. Required because the production service calls
-/// [getApplicationDocumentsDirectory] / [getApplicationSupportDirectory] —
-/// both of which fail outside an app context unless the platform interface
-/// is mocked.
-class _FakePathProvider extends PathProviderPlatform with MockPlatformInterfaceMixin {
-  _FakePathProvider(this.root);
-
-  final Directory root;
-  String get _docs => p.join(root.path, 'documents');
-  String get _support => p.join(root.path, 'support');
-  String get _cache => p.join(root.path, 'cache');
-  String get _temp => p.join(root.path, 'temp');
-
-  @override
-  Future<String?> getApplicationDocumentsPath() async => _ensure(_docs);
-
-  @override
-  Future<String?> getApplicationSupportPath() async => _ensure(_support);
-
-  @override
-  Future<String?> getApplicationCachePath() async => _ensure(_cache);
-
-  @override
-  Future<String?> getTemporaryPath() async => _ensure(_temp);
-
-  String _ensure(String dir) {
-    Directory(dir).createSync(recursive: true);
-    return dir;
-  }
-}
-
 void main() {
   late Directory tmpRoot;
 
@@ -53,7 +21,7 @@ void main() {
     SettingsService.resetForTesting();
     DownloadStorageService.resetForTesting();
     tmpRoot = await Directory.systemTemp.createTemp('dss_test_');
-    PathProviderPlatform.instance = _FakePathProvider(tmpRoot);
+    PathProviderPlatform.instance = FakePathProvider(tmpRoot);
   });
 
   tearDown(() async {

test/services/jellyfin_auth_service_test.dart

@@ -12,6 +12,8 @@ import 'package:plezy/services/jellyfin_endpoint_discovery.dart';
 import 'package:plezy/utils/log_redaction_manager.dart';
 import 'package:plezy/utils/media_server_timeouts.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+
 /// Helpers for stubbing http responses keyed by request path.
 typedef _Handler = FutureOr<http.Response> Function(http.BaseRequest req);
 
@@ -20,12 +22,7 @@ http.Response _bareOk(String body) => http.Response(body, 200, headers: {'conten
 http.Response _status(int code, [Object? json]) =>
     http.Response(json == null ? '' : jsonEncode(json), code, headers: {'content-type': 'application/json'});
 
-JellyfinConnection _existingConn({String accessToken = 'tok-old'}) => JellyfinConnection(
-  id: 'srv-1/user-1',
-  baseUrl: 'https://jf.example.com',
-  serverName: 'Home',
-  serverMachineId: 'srv-1',
-  userId: 'user-1',
+JellyfinConnection _existingConn({String accessToken = 'tok-old'}) => testJellyfinConnection(
   userName: 'edde',
   accessToken: accessToken,
   deviceId: 'dev-xyz',

test/services/jellyfin_client_failures_test.dart

@@ -11,20 +11,18 @@ import 'package:plezy/exceptions/media_server_exceptions.dart';
 import 'package:plezy/services/jellyfin_api_cache.dart';
 import 'package:plezy/services/jellyfin_client.dart';
 
-JellyfinConnection _conn({String baseUrl = 'https://jf.example.com', List<String>? baseUrls}) => JellyfinConnection(
-  id: 'srv-1/user-1',
+import '../test_helpers/backend_client_fixtures.dart';
+
+JellyfinConnection _conn({String baseUrl = 'https://jf.example.com', List<String>? baseUrls}) => testJellyfinConnection(
   baseUrl: baseUrl,
   baseUrls: baseUrls,
-  serverName: 'Home',
-  serverMachineId: 'srv-1',
-  userId: 'user-1',
   userName: 'edde',
   accessToken: 'tok-abc',
   deviceId: 'dev-xyz',
   createdAt: DateTime.fromMillisecondsSinceEpoch(0),
 );
 
-JellyfinClient _withMock(MockClient mock) => JellyfinClient.forTesting(connection: _conn(), httpClient: mock);
+JellyfinClient _withMock(MockClient mock) => testJellyfinClient(connection: _conn(), httpClient: mock);
 
 /// Failure-path coverage for the Jellyfin HTTP layer.
 ///

test/services/jellyfin_client_urls_test.dart

@@ -14,13 +14,12 @@ import 'package:plezy/services/jellyfin_client.dart';
 import 'package:plezy/services/playback_initialization_types.dart';
 import 'package:plezy/utils/device_identity.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+import '../test_helpers/paged_fakes.dart';
+
 JellyfinConnection _conn({String accessToken = 'tok-abc', String baseUrl = 'https://jf.example.com'}) =>
-    JellyfinConnection(
-      id: 'srv-1/user-1',
+    testJellyfinConnection(
       baseUrl: baseUrl,
-      serverName: 'Home',
-      serverMachineId: 'srv-1',
-      userId: 'user-1',
       userName: 'edde',
       accessToken: accessToken,
       deviceId: 'dev-xyz',
@@ -3282,7 +3281,10 @@ void main() {
           final start = int.parse(req.url.queryParameters['StartIndex'] ?? '0');
           final limit = int.parse(req.url.queryParameters['Limit'] ?? '2');
           return http.Response(
-            jsonEncode({'Items': allItems.skip(start).take(limit).toList(), 'TotalRecordCount': allItems.length}),
+            jsonEncode({
+              'Items': sliceFakePage(allItems, start: start, size: limit),
+              'TotalRecordCount': allItems.length,
+            }),
             200,
             headers: {'content-type': 'application/json'},
           );

test/services/jellyfin_favorites_isolation_test.dart

@@ -7,25 +7,23 @@ import 'package:plezy/models/livetv_channel.dart';
 import 'package:plezy/services/jellyfin_client.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
 import '../test_helpers/prefs.dart';
 
-JellyfinConnection _conn({required String userId}) => JellyfinConnection(
-  id: 'srv-shared/$userId',
-  baseUrl: 'https://jf.example.com',
-  serverName: 'Shared JF',
-  serverMachineId: 'srv-shared',
+JellyfinConnection _conn({required String userId}) => testJellyfinConnection(
+  machineId: 'srv-shared',
   userId: userId,
+  serverName: 'Shared JF',
   userName: 'user-$userId',
   accessToken: 'tok-$userId',
   deviceId: 'dev-$userId',
   createdAt: DateTime.fromMillisecondsSinceEpoch(0),
 );
 
-JellyfinClient _client(JellyfinConnection conn) => JellyfinClient.forTesting(
+JellyfinClient _client(JellyfinConnection conn) => testJellyfinClient(
   connection: conn,
-  // Favorites read path is local-only; an http stub that always 500s is
-  // fine since fetchFavoriteChannels never hits it.
-  httpClient: MockClient((_) async => throw StateError('no HTTP expected')),
+  // Favorites read path is local-only; any HTTP call is a test failure.
+  handler: (_) async => throw StateError('no HTTP expected'),
 );
 
 String _favKey(JellyfinConnection conn) => 'jellyfin_fav_channels:${conn.id}';

test/services/jellyfin_music_mapper_test.dart

@@ -9,6 +9,8 @@ import 'package:plezy/media/media_kind.dart';
 import 'package:plezy/services/jellyfin_client.dart';
 import 'package:plezy/services/jellyfin_mappers.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+
 const _serverId = 'jf-machine-1';
 
 /// Captured (trimmed) from a live Jellyfin 10.11 server — an `Audio` row
@@ -65,12 +67,7 @@ Map<String, dynamic> _albumJson() => {
   'MediaType': 'Unknown',
 };
 
-JellyfinConnection _conn() => JellyfinConnection(
-  id: 'srv-1/user-1',
-  baseUrl: 'https://jf.example.com',
-  serverName: 'Home',
-  serverMachineId: 'srv-1',
-  userId: 'user-1',
+JellyfinConnection _conn() => testJellyfinConnection(
   userName: 'edde',
   accessToken: 'tok-abc',
   deviceId: 'dev-xyz',

test/services/jellyfin_playback_bundle_test.dart

@@ -10,12 +10,9 @@ import 'package:plezy/services/jellyfin_api_cache.dart';
 import 'package:plezy/services/jellyfin_client.dart';
 import 'package:plezy/services/plex_api_cache.dart';
 
-JellyfinConnection _conn() => JellyfinConnection(
-  id: 'srv-1/user-1',
-  baseUrl: 'https://jf.example.com',
-  serverName: 'Home',
-  serverMachineId: 'srv-1',
-  userId: 'user-1',
+import '../test_helpers/backend_client_fixtures.dart';
+
+JellyfinConnection _conn() => testJellyfinConnection(
   userName: 'edde',
   accessToken: 'tok-abc',
   deviceId: 'dev-xyz',
@@ -44,10 +41,10 @@ void main() {
   });
 
   JellyfinClient buildClient(String body) {
-    final mock = MockClient((req) async {
-      return http.Response(body, 200, headers: {'content-type': 'application/json'});
-    });
-    return JellyfinClient.forTesting(connection: _conn(), httpClient: mock);
+    return testJellyfinClient(
+      connection: _conn(),
+      handler: (_) async => http.Response(body, 200, headers: {'content-type': 'application/json'}),
+    );
   }
 
   group('JellyfinClient.fetchPlaybackBundle', () {

test/services/jellyfin_sequential_launcher_test.dart

@@ -13,6 +13,8 @@ import 'package:plezy/services/media_list_playback_launcher.dart';
 import 'package:plezy/services/playlist_items_loader.dart';
 import 'package:plezy/utils/media_server_http_client.dart';
 
+import '../test_helpers/paged_fakes.dart';
+
 /// Recording fake that satisfies [JellyfinClient] via `implements` +
 /// `noSuchMethod`. The launcher only needs the
 /// [MediaServerClient.fetchPlayableDescendants] /
@@ -62,17 +64,9 @@ class _RecordingJellyfinClient implements JellyfinClient {
   @override
   Future<LibraryPage<MediaItem>> fetchPlaylistPage(String id, {int? start, int? size, AbortController? abort}) async {
     final offset = start ?? 0;
-    final limit = size ?? 100;
+    final limit = size ?? fakeMediaPageSize;
     fetchPlaylistItemsCalls.add((id: id, offset: offset, limit: limit));
-    if (offset >= playlistItemsResponse.length) {
-      return LibraryPage<MediaItem>(items: const [], totalCount: playlistItemsResponse.length, offset: offset);
-    }
-    final end = (offset + limit).clamp(0, playlistItemsResponse.length);
-    return LibraryPage<MediaItem>(
-      items: playlistItemsResponse.sublist(offset, end),
-      totalCount: playlistItemsResponse.length,
-      offset: offset,
-    );
+    return fakeLibraryPage(playlistItemsResponse, start: start, size: size);
   }
 
   @override

test/services/jellyfin_trickplay_service_test.dart

@@ -10,12 +10,9 @@ import 'package:plezy/services/jellyfin_trickplay_service.dart';
 import 'package:plezy/services/scrub_preview_source.dart';
 import 'package:plezy/utils/device_identity.dart';
 
-JellyfinConnection _conn() => JellyfinConnection(
-  id: 'srv-1/user-1',
-  baseUrl: 'https://jf.example.com',
-  serverName: 'Home',
-  serverMachineId: 'srv-1',
-  userId: 'user-1',
+import '../test_helpers/backend_client_fixtures.dart';
+
+JellyfinConnection _conn() => testJellyfinConnection(
   userName: 'edde',
   accessToken: 'tok-abc',
   deviceId: 'dev-xyz',

test/services/live_tv_capability_contract_test.dart

@@ -8,7 +8,6 @@ import 'package:plezy/connection/connection.dart';
 import 'package:plezy/database/app_database.dart';
 import 'package:plezy/media/ids.dart';
 import 'package:plezy/media/media_server_client.dart';
-import 'package:plezy/models/plex/plex_config.dart';
 import 'package:plezy/providers/multi_server_provider.dart';
 import 'package:plezy/services/data_aggregation_service.dart';
 import 'package:plezy/services/jellyfin_client.dart';
@@ -16,6 +15,8 @@ import 'package:plezy/services/multi_server_manager.dart';
 import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/plex_client.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+
 void main() {
   late AppDatabase db;
 
@@ -26,29 +27,19 @@ void main() {
 
   tearDown(() => db.close());
 
-  PlexClient plexClient(http.Client httpClient) => PlexClient.forTesting(
-    config: PlexConfig(
-      baseUrl: 'https://plex.example.com',
-      token: 'plex-token',
-      clientIdentifier: 'plex-device',
-      product: 'Plezy',
-      version: '1',
-      machineIdentifier: 'plex-machine',
-    ),
+  PlexClient plexClient(http.Client httpClient) => testPlexClient(
+    config: testPlexConfig(token: 'plex-token', clientIdentifier: 'plex-device', machineIdentifier: 'plex-machine'),
     serverId: ServerId('plex-machine'),
     httpClient: httpClient,
   );
 
-  JellyfinClient jellyfinClient(http.Client httpClient) => JellyfinClient.forTesting(
-    connection: JellyfinConnection(
-      id: 'jellyfin-machine/user-1',
+  JellyfinClient jellyfinClient(http.Client httpClient) => testJellyfinClient(
+    connection: testJellyfinConnection(
+      machineId: 'jellyfin-machine',
+      userId: 'user-1',
       baseUrl: 'https://jellyfin.example.com',
       serverName: 'Jellyfin',
-      serverMachineId: 'jellyfin-machine',
-      userId: 'user-1',
-      userName: 'User',
       accessToken: 'jellyfin-token',
-      deviceId: 'device-1',
       createdAt: DateTime.fromMillisecondsSinceEpoch(0),
     ),
     httpClient: httpClient,

test/services/multi_server_manager_test.dart

@@ -14,24 +14,20 @@ import 'package:plezy/services/plex_client.dart';
 import 'package:plezy/services/jellyfin_client.dart';
 import 'package:plezy/services/multi_server_manager.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
 import '../test_helpers/prefs.dart';
 
-JellyfinConnection _jellyfinConnection(String userId) => JellyfinConnection(
-  id: 'jf-machine/$userId',
-  baseUrl: 'https://jf.example.com',
-  serverName: 'Shared JF',
-  serverMachineId: 'jf-machine',
+JellyfinConnection _jellyfinConnection(String userId) => testJellyfinConnection(
+  machineId: 'jf-machine',
   userId: userId,
+  serverName: 'Shared JF',
   userName: userId,
   accessToken: 'token-$userId',
   deviceId: 'device',
   createdAt: DateTime.fromMillisecondsSinceEpoch(0),
 );
 
-JellyfinClient _jellyfinClient(String userId) => JellyfinClient.forTesting(
-  connection: _jellyfinConnection(userId),
-  httpClient: MockClient((_) async => http.Response('{}', 200)),
-);
+JellyfinClient _jellyfinClient(String userId) => testJellyfinClient(connection: _jellyfinConnection(userId));
 
 // NOTE on coverage scope:
 // [MultiServerManager.addServer] / `connectToAllServers` / `_createClientForServer`

test/services/offline_watch_sync_service_test.dart

@@ -19,6 +19,7 @@ import 'package:plezy/services/offline_mode_source.dart';
 import 'package:plezy/services/offline_watch_sync_service.dart';
 import 'package:plezy/utils/watch_state_notifier.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
 import '../test_helpers/prefs.dart';
 
 // NOTE on coverage scope:
@@ -154,12 +155,10 @@ class _ScopedRecordingMediaClient extends _RecordingMediaClient implements Scope
   return (svc: svc, db: db, mgr: mgr);
 }
 
-JellyfinConnection _jellyfinConnection(String userId) => JellyfinConnection(
-  id: 'jf-machine/$userId',
-  baseUrl: 'https://jf.example.com',
-  serverName: 'Shared JF',
-  serverMachineId: 'jf-machine',
+JellyfinConnection _jellyfinConnection(String userId) => testJellyfinConnection(
+  machineId: 'jf-machine',
   userId: userId,
+  serverName: 'Shared JF',
   userName: userId,
   accessToken: 'token-$userId',
   deviceId: 'device',

test/services/playback_initialization_offline_cache_test.dart

@@ -5,7 +5,6 @@ import 'dart:io';
 import 'package:drift/drift.dart';
 import 'package:drift/native.dart';
 import 'package:flutter_test/flutter_test.dart';
-import 'package:path/path.dart' as p;
 import 'package:path_provider_platform_interface/path_provider_platform_interface.dart';
 import 'package:plezy/database/app_database.dart';
 import 'package:plezy/media/media_backend.dart';
@@ -21,37 +20,10 @@ import 'package:plezy/services/playback_initialization_service.dart';
 import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/plex_mappers.dart';
 import 'package:plezy/services/settings_service.dart';
-import 'package:plugin_platform_interface/plugin_platform_interface.dart';
 
+import '../test_helpers/io_fakes.dart';
 import '../test_helpers/prefs.dart';
 
-class _FakePathProvider extends PathProviderPlatform with MockPlatformInterfaceMixin {
-  _FakePathProvider(this.root);
-
-  final Directory root;
-  String get _docs => p.join(root.path, 'documents');
-  String get _support => p.join(root.path, 'support');
-  String get _cache => p.join(root.path, 'cache');
-  String get _temp => p.join(root.path, 'temp');
-
-  @override
-  Future<String?> getApplicationDocumentsPath() async => _ensure(_docs);
-
-  @override
-  Future<String?> getApplicationSupportPath() async => _ensure(_support);
-
-  @override
-  Future<String?> getApplicationCachePath() async => _ensure(_cache);
-
-  @override
-  Future<String?> getTemporaryPath() async => _ensure(_temp);
-
-  String _ensure(String dir) {
-    Directory(dir).createSync(recursive: true);
-    return dir;
-  }
-}
-
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
 
@@ -63,7 +35,7 @@ void main() {
     SettingsService.resetForTesting();
     DownloadStorageService.resetForTesting();
     tmpRoot = await Directory.systemTemp.createTemp('playback_init_test_');
-    PathProviderPlatform.instance = _FakePathProvider(tmpRoot);
+    PathProviderPlatform.instance = FakePathProvider(tmpRoot);
     db = AppDatabase.forTesting(NativeDatabase.memory());
     PlexApiCache.initialize(db);
     JellyfinApiCache.initialize(db);

test/services/plex_client_http_contract_test.dart

@@ -3,14 +3,14 @@ import 'dart:convert';
 import 'package:drift/native.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:http/http.dart' as http;
-import 'package:http/testing.dart';
 import 'package:plezy/database/app_database.dart';
 import 'package:plezy/exceptions/media_server_exceptions.dart';
 import 'package:plezy/media/ids.dart';
-import 'package:plezy/models/plex/plex_config.dart';
 import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/plex_client.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+
 void main() {
   late AppDatabase db;
 
@@ -21,19 +21,8 @@ void main() {
 
   tearDown(() => db.close());
 
-  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) {
-    return PlexClient.forTesting(
-      config: PlexConfig(
-        baseUrl: 'https://plex.example.com',
-        token: 'token',
-        clientIdentifier: 'client-id',
-        product: 'Plezy',
-        version: '1',
-      ),
-      serverId: ServerId('server-id'),
-      httpClient: MockClient(handler),
-    );
-  }
+  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) =>
+      testPlexClient(serverId: ServerId('server-id'), handler: handler);
 
   test('void mutations surface non-success responses', () async {
     final client = makeClient((_) async => http.Response('rejected', 500));

test/services/plex_library_details_test.dart

@@ -4,13 +4,13 @@ import 'package:plezy/media/ids.dart';
 import 'package:drift/native.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:http/http.dart' as http;
-import 'package:http/testing.dart';
 import 'package:plezy/database/app_database.dart';
 import 'package:plezy/media/library_query.dart';
-import 'package:plezy/models/plex/plex_config.dart';
 import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/plex_client.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+
 void main() {
   late AppDatabase db;
 
@@ -23,19 +23,8 @@ void main() {
     await db.close();
   });
 
-  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) {
-    return PlexClient.forTesting(
-      config: PlexConfig(
-        baseUrl: 'https://plex.example.com',
-        token: 'token',
-        clientIdentifier: 'client-id',
-        product: 'Plezy',
-        version: '1',
-      ),
-      serverId: ServerId('server-id'),
-      httpClient: MockClient(handler),
-    );
-  }
+  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) =>
+      testPlexClient(serverId: ServerId('server-id'), handler: handler);
 
   test('filters and sorts use dedicated Plex endpoints', () async {
     final requests = <Uri>[];

test/services/plex_music_transcode_test.dart

@@ -1,14 +1,14 @@
 import 'package:drift/native.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:http/http.dart' as http;
-import 'package:http/testing.dart';
 import 'package:plezy/database/app_database.dart';
 import 'package:plezy/media/ids.dart';
 import 'package:plezy/models/audio_quality_preset.dart';
-import 'package:plezy/models/plex/plex_config.dart';
 import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/plex_client.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+
 void main() {
   late AppDatabase db;
 
@@ -21,19 +21,8 @@ void main() {
     await db.close();
   });
 
-  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) {
-    return PlexClient.forTesting(
-      config: PlexConfig(
-        baseUrl: 'https://plex.example.com',
-        token: 'token',
-        clientIdentifier: 'client-id',
-        product: 'Plezy',
-        version: '1',
-      ),
-      serverId: ServerId('server-id'),
-      httpClient: MockClient(handler),
-    );
-  }
+  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) =>
+      testPlexClient(serverId: ServerId('server-id'), handler: handler);
 
   test('music transcode params cap bitrate and carry the musicProfile target', () {
     final client = makeClient((_) async => http.Response('not used', 500));

test/services/plex_playback_data_request_test.dart

@@ -4,19 +4,19 @@ import 'package:plezy/media/ids.dart';
 import 'package:drift/native.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:http/http.dart' as http;
-import 'package:http/testing.dart';
 import 'package:plezy/database/app_database.dart';
 import 'package:plezy/media/media_backend.dart';
 import 'package:plezy/media/media_item.dart';
 import 'package:plezy/media/media_kind.dart';
 import 'package:plezy/media/media_source_info.dart';
 import 'package:plezy/mpv/mpv.dart';
-import 'package:plezy/models/plex/plex_config.dart';
 import 'package:plezy/models/transcode_quality_preset.dart';
 import 'package:plezy/services/playback_initialization_types.dart';
 import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/plex_client.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+
 void main() {
   late AppDatabase db;
 
@@ -29,19 +29,8 @@ void main() {
     await db.close();
   });
 
-  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) {
-    return PlexClient.forTesting(
-      config: PlexConfig(
-        baseUrl: 'https://plex.example.com',
-        token: 'token',
-        clientIdentifier: 'client-id',
-        product: 'Plezy',
-        version: '1',
-      ),
-      serverId: ServerId('server-id'),
-      httpClient: MockClient(handler),
-    );
-  }
+  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) =>
+      testPlexClient(serverId: ServerId('server-id'), handler: handler);
 
   MediaSourceInfo mediaInfoWithSubtitles(List<MediaSubtitleTrack> subtitleTracks) {
     return MediaSourceInfo(

test/services/plex_search_test.dart

@@ -4,12 +4,12 @@ import 'package:plezy/media/ids.dart';
 import 'package:drift/native.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:http/http.dart' as http;
-import 'package:http/testing.dart';
 import 'package:plezy/database/app_database.dart';
-import 'package:plezy/models/plex/plex_config.dart';
 import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/plex_client.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+
 http.Response _json(Object body) => http.Response(jsonEncode(body), 200, headers: {'content-type': 'application/json'});
 
 void main() {
@@ -24,20 +24,8 @@ void main() {
     await db.close();
   });
 
-  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) {
-    return PlexClient.forTesting(
-      config: PlexConfig(
-        baseUrl: 'https://plex.example.com',
-        token: 'token',
-        clientIdentifier: 'client-id',
-        product: 'Plezy',
-        version: 'test',
-      ),
-      serverId: ServerId('plex-1'),
-      serverName: 'Plex',
-      httpClient: MockClient(handler),
-    );
-  }
+  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) =>
+      testPlexClient(serverId: ServerId('plex-1'), serverName: 'Plex', handler: handler);
 
   test('search defaults to 100 movie, TV, and music candidates', () async {
     final captured = <Uri>[];

test/services/plex_timeline_session_test.dart

@@ -3,18 +3,18 @@ import 'dart:convert';
 import 'package:drift/native.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:http/http.dart' as http;
-import 'package:http/testing.dart';
 import 'package:plezy/database/app_database.dart';
 import 'package:plezy/media/ids.dart';
 import 'package:plezy/media/media_backend.dart';
 import 'package:plezy/media/media_item.dart';
 import 'package:plezy/media/media_kind.dart';
-import 'package:plezy/models/plex/plex_config.dart';
 import 'package:plezy/models/transcode_quality_preset.dart';
 import 'package:plezy/services/playback_initialization_types.dart';
 import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/plex_client.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+
 /// Regression coverage for the Plex transcode reporting bug: while
 /// transcoding, the `/:/timeline` reports must carry the playback's
 /// `X-Plex-Session-Identifier` so the server correlates the timeline with the
@@ -32,19 +32,8 @@ void main() {
     await db.close();
   });
 
-  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) {
-    return PlexClient.forTesting(
-      config: PlexConfig(
-        baseUrl: 'https://plex.example.com',
-        token: 'token',
-        clientIdentifier: 'client-id',
-        product: 'Plezy',
-        version: '1',
-      ),
-      serverId: ServerId('server-id'),
-      httpClient: MockClient(handler),
-    );
-  }
+  PlexClient makeClient(Future<http.Response> Function(http.Request request) handler) =>
+      testPlexClient(serverId: ServerId('server-id'), handler: handler);
 
   /// Captures every request and answers `/:/timeline` with 200 so
   /// [PlexClient.updateProgress]'s `throwIfHttpError` is satisfied.

test/services/plex_transcoder_capability_test.dart

@@ -5,12 +5,12 @@ import 'dart:io';
 import 'package:drift/native.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:http/http.dart' as http;
-import 'package:http/testing.dart';
 import 'package:plezy/database/app_database.dart';
-import 'package:plezy/models/plex/plex_config.dart';
 import 'package:plezy/services/plex_api_cache.dart';
 import 'package:plezy/services/plex_client.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
+
 void main() {
   late AppDatabase db;
 
@@ -77,23 +77,16 @@ void main() {
 }
 
 PlexClient _makeClient(Map<String, dynamic> rootContainer) {
-  return PlexClient.forTesting(
-    config: PlexConfig(
-      baseUrl: 'https://plex.example.com',
-      token: 'token',
-      clientIdentifier: 'client-id',
-      product: 'Plezy',
-      version: 'test',
-    ),
+  return testPlexClient(
     serverId: ServerId('server-id'),
-    httpClient: MockClient((request) async {
+    handler: (request) async {
       expect(request.url.path, '/');
       return http.Response(
         jsonEncode({'MediaContainer': rootContainer}),
         200,
         headers: {'content-type': 'application/json'},
       );
-    }),
+    },
   );
 }
 

test/services/sync_rule_executor_test.dart

@@ -17,14 +17,13 @@ import 'package:plezy/services/jellyfin_client.dart';
 import 'package:plezy/services/multi_server_manager.dart';
 import 'package:plezy/services/sync_rule_executor.dart';
 
+import '../test_helpers/backend_client_fixtures.dart';
 import '../test_helpers/prefs.dart';
 
-JellyfinConnection _jellyfinConnection(String userId) => JellyfinConnection(
-  id: 'jf-machine/$userId',
-  baseUrl: 'https://jf.example.com',
-  serverName: 'Shared JF',
-  serverMachineId: 'jf-machine',
+JellyfinConnection _jellyfinConnection(String userId) => testJellyfinConnection(
+  machineId: 'jf-machine',
   userId: userId,
+  serverName: 'Shared JF',
   userName: userId,
   accessToken: 'token-$userId',
   deviceId: 'device',