VariableLog.php

<?php

/**
 * @file
 * Definition of Drupal\Core\Mail\VariableLog.
 */
namespace Drupal\Core\Mail;


/**
 * Defines a mail sending implementation that captures sent messages to a
 * variable.
 *
 * This class is for running tests or for development.
 */
class VariableLog extends PhpMail implements MailInterface {

  /**
   * Overrides Drupal\Core\Mail\PhpMail::mail().
   *
   * Accepts an e-mail message and store it in a variable.
   */
  public function mail(array $message) {
    $captured_emails = state()
      ->get('system.test_email_collector') ?: array();
    $captured_emails[] = $message;
    state()
      ->set('system.test_email_collector', $captured_emails);
    return TRUE;
  }

}