InvalidConfig exception in test after upgrade from Laravel 11 to 12

[giovanniledda]

I've recently upgraded to Laravel 12 then to spatie/laravel-backup:"^9.0" to meet the framework requirements.
Before this change, all my tests were green; now 90% of them are broken, and this is the message I get:

  at vendor/spatie/laravel-backup/src/Exceptions/InvalidConfig.php:16
     12▕     }
     13▕
     14▕     public static function missingSender(): static
     15▕     {
  ➜  16▕         return new static("No sender email address specified. Make sure it's set in your config file or as `MAIL_FROM_ADDRESS` in your .env file.");
     17▕     }
     18▕
     19▕     public static function integerMustBePositive(string $name): static
     20▕     {

      +25 vendor frames
  26  tests/TestCase.php:39

In .env.testing, if I change:
MAIL_FROM_ADDRESS=null
in
MAIL_FROM_ADDRESS=[email protected]
..then tests become green.

My point is: is it normal to have that email check inside tests after an upgrade?
Anyone with the same problem?
Thank you!