def METHOD_NAME(self):
    subject = "sübjèçt"
    body = "bödÿ-àéïöñß"
    attach = BytesIO()
    attach.write(body.encode("utf-8"))
    attach.seek(0)
    attachs = [("attachment", "text/plain", attach)]
    mailsender = MailSender(debug=True)
    mailsender.send(
        to=["test@scrapy.org"],
        subject=subject,
        body=body,
        attachs=attachs,
        charset="utf-8",
        _callback=self._catch_mail_sent,
    )
    assert self.catched_msg
    self.assertEqual(self.catched_msg["subject"], subject)
    self.assertEqual(self.catched_msg["body"], body)
    msg = self.catched_msg["msg"]
    self.assertEqual(msg["subject"], subject)
    self.assertEqual(msg.get_charset(), Charset("utf-8"))
    self.assertEqual(msg.get("Content-Type"), 'multipart/mixed; charset="utf-8"')
    payload = msg.get_payload()
    assert isinstance(payload, list)
    self.assertEqual(len(payload), 2)
    text, attach = payload
    self.assertEqual(text.get_payload(decode=True).decode("utf-8"), body)
    self.assertEqual(text.get_charset(), Charset("utf-8"))
    self.assertEqual(attach.get_payload(decode=True).decode("utf-8"), body)