refactor: reduce model and focus boilerplate

test/models/json_model_round_trip_test.dart

@@ -0,0 +1,71 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/models/companion_remote/remote_command.dart';
+import 'package:plezy/models/mpv_config_models.dart';
+import 'package:plezy/models/trakt/trakt_ids.dart';
+import 'package:plezy/watch_together/models/watch_session.dart';
+import 'package:plezy/watch_together/services/recent_rooms_service.dart';
+
+void main() {
+  group('JSON model round trips', () {
+    test('MpvPreset preserves ISO timestamp shape', () {
+      final createdAt = DateTime.utc(2024, 1, 2, 3, 4, 5);
+      final preset = MpvPreset(name: 'Anime', text: 'profile=gpu-hq', createdAt: createdAt);
+
+      expect(preset.toJson(), {'name': 'Anime', 'text': 'profile=gpu-hq', 'createdAt': createdAt.toIso8601String()});
+
+      final decoded = MpvPreset.fromJson(preset.toJson());
+      expect(decoded.name, preset.name);
+      expect(decoded.text, preset.text);
+      expect(decoded.createdAt, createdAt);
+    });
+
+    test('TraktIds omits null fields and accepts numeric ids', () {
+      const ids = TraktIds(imdb: 'tt123', tmdb: 42);
+
+      expect(ids.toJson(), {'imdb': 'tt123', 'tmdb': 42});
+
+      final decoded = TraktIds.fromJson({'trakt': 1.0, 'slug': 'movie', 'tmdb': 42.0, 'tvdb': 9});
+      expect(decoded.trakt, 1);
+      expect(decoded.slug, 'movie');
+      expect(decoded.tmdb, 42);
+      expect(decoded.tvdb, 9);
+      expect(decoded.hasAny, isTrue);
+    });
+
+    test('RecentRoom preserves epoch timestamp and control mode index', () {
+      final lastUsed = DateTime.fromMillisecondsSinceEpoch(1700000000000);
+      final room = RecentRoom(code: 'ABCD', name: 'Movie night', lastUsed: lastUsed, controlMode: ControlMode.anyone);
+
+      expect(room.toJson(), {'code': 'ABCD', 'name': 'Movie night', 'lastUsed': 1700000000000, 'controlMode': 1});
+
+      final decoded = RecentRoom.fromJson(room.toJson());
+      expect(decoded.code, room.code);
+      expect(decoded.name, room.name);
+      expect(decoded.lastUsed, lastUsed);
+      expect(decoded.controlMode, ControlMode.anyone);
+    });
+
+    test('RecentRoom omits nullable fields when absent', () {
+      final lastUsed = DateTime.fromMillisecondsSinceEpoch(1700000000000);
+      final room = RecentRoom(code: 'ABCD', lastUsed: lastUsed);
+
+      expect(room.toJson(), {'code': 'ABCD', 'lastUsed': 1700000000000});
+    });
+
+    test('RemoteCommand keeps compact protocol keys and unknown fallback', () {
+      const command = RemoteCommand(type: RemoteCommandType.volumeSet, data: {'value': 50});
+
+      expect(command.toJson(), {
+        't': RemoteCommandType.volumeSet.index,
+        'd': {'value': 50},
+      });
+
+      final decoded = RemoteCommand.fromJson(command.toJson());
+      expect(decoded.type, RemoteCommandType.volumeSet);
+      expect(decoded.data, {'value': 50});
+
+      final unknown = RemoteCommand.fromJson({'t': 999});
+      expect(unknown.type, RemoteCommandType.ping);
+    });
+  });
+}