Test sent emails in Laravel 8. Applied to test emails sent by Mail or Notification facades.

SentMailsTest.php

<?php

namespace Tests;

use App\User;
use Tests\TestCase;
use Illuminate\Notifications\Notification;

class MyNotification extends Notification
{
    public function via($notifiable)
    {
        return ['mail'];
    }

    public function toMail($notifiable)
    {
        return (new MailMessage())
            ->subject('Test mail')
            ->line('Test mail');
    }
}

class SentMailsTest extends TestCase
{
   protected function setUp(): void
    {
        parent::setUp();
        $this->user = (new User())
            ->fill(['email' => 'test@example.com']);

        $this->sentMails = app('mailer')
            ->getSwiftMailer()
            ->getTransport()
            ->messages();
    }
  
    public function test_should_notification_sends_email()
    {
        $this->user->notify(new MyNotification());

        $this->assertCount(1, $this->sentMails, 'Email should be sent');
        $mail = $this->sentMails[0];
      
        $this->assertArrayHasKey('test@example.com', $mail->getTo());
        $this->assertStringContainsString('Test mail', $mail->getBody());
    }  
}