I'm looking for the same answer, trying to figure out how to test sendPasswordResetNotification().
See https://github.com/laravel/framework/issues/15721#issuecomment-251145812 I found @themsaid 's posts, where he said it should work?!
I guess, it may be the lack of the missing callback paramter in assertSentTo(). When I try to run the test with
Notification::hasSent($user, ResetPassword::class);
the test passed with OK.
/**
* Assert if a notification was sent based on a truth-test callback.
*
* @param mixed $notifiable
* @param string $notification
* @param callable|null $callback
* @return void
*/
public function assertSentTo($notifiable, $notification, $callback = null)