Laravel Serialization of 'UploadFile' class is not allowed

Running tests written by other programmers and encountered the following error:

ErrorException: Serialization of closure failed: Serialization of 'Symfony\Component\HttpFoundation\File\UploadedFile' is not allowed

/home/vagrant/Code/punto/vendor/jeremeamia/SuperClosure/src/SerializableClosure.php:116
/home/vagrant/Code/punto/vendor/jeremeamia/SuperClosure/src/Serializer.php:69
/home/vagrant/Code/punto/vendor/laravel/framework/src/Illuminate/Mail/Mailer.php:272
/home/vagrant/Code/punto/vendor/laravel/framework/src/Illuminate/Mail/Mailer.php:193
/home/vagrant/Code/punto/vendor/laravel/framework/src/Illuminate/Support/Facades/Facade.php:219
/home/vagrant/Code/punto/app/Services/NotificationService.php:126
/home/vagrant/Code/punto/app/Exceptions/Handler.php:42
/home/vagrant/Code/punto/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php:269
/home/vagrant/Code/punto/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php:89
/home/vagrant/Code/punto/vendor/laravel/framework/src/Illuminate/Foundation/Testing/CrawlerTrait.php:394

I am not familiar with the system yet. This error seems like I have to implement Serialization to some class.

via Chebli Mohamed