Mail attachments seem to live at $mail['params']['attachments']. Test coverage is not included due to Drupal\DrupalExtension\Context\MailContext::drupalSendsMail() relying on Drupal\Driver\DriverInterface::sendMail(), which appears to have no support for the direct inclusion of attachments, nor support for adding mail parameters like 'attachments'.
Resolves #672.
Mail attachments seem to live at
$mail['params']['attachments']. Test coverage is not included due to Drupal\DrupalExtension\Context\MailContext::drupalSendsMail() relying on Drupal\Driver\DriverInterface::sendMail(), which appears to have no support for the direct inclusion of attachments, nor support for adding mail parameters like 'attachments'.