def METHOD_NAME(self):
    """
    Check that the "Validate, export and send to SdI" button
    sends the e-invoice.
    """
    # Arrange: create a draft invoice with no attachment
    invoice = self._create_invoice()
    self._create_fetchmail_pec_server()
    self.assertEqual(invoice.state, "draft")
    self.assertFalse(invoice.fatturapa_attachment_out_id)
    # Act: open, export and send the invoice
    invoice.action_open_export_send_sdi()
    e_invoice = invoice.fatturapa_attachment_out_id
    self.assertEqual(e_invoice.state, "sent")