feat(tests): updated tests coverage to 66.5%

test/features/chat/models/chat_message_model_test.dart

@@ -43,6 +43,50 @@ void main() {
       expect(model.mediaData, isNotNull);
       expect(model.mediaData!.length, 1);
     });
+
+    test('toJson serializes ChatMessageModel correctly', () {
+      final model = ChatMessageModel(
+        id: 1,
+        data: 'Test message',
+        mediaData: null,
+        authorId: 123,
+        updatedAt: DateTime(2024, 1, 1, 12, 0, 0),
+        isRead: false,
+        isCurrentUserAuthor: true,
+        roomId: 'room-1',
+        type: 'text',
+      );
+
+      final json = model.toJson();
+
+      expect(json['id'], 1);
+      expect(json['data'], 'Test message');
+      expect(json['author_id'], 123);
+      expect(json['read_by_to_user'], false);
+      expect(json['is_author_message_auth_user'], true);
+      expect(json['room_id'], 'room-1');
+      expect(json['type'], 'text');
+    });
+
+    test('toJson handles null fields correctly', () {
+      final model = ChatMessageModel(
+        id: 1,
+        data: 'Test message',
+        mediaData: null,
+        authorId: 123,
+        updatedAt: DateTime(2024, 1, 1, 12, 0, 0),
+        isRead: false,
+        isCurrentUserAuthor: null,
+        roomId: null,
+        type: null,
+      );
+
+      final json = model.toJson();
+
+      expect(json['is_author_message_auth_user'], isNull);
+      expect(json['room_id'], isNull);
+      expect(json['type'], isNull);
+    });
   });
 }