def METHOD_NAME(self):
    coupon = Coupon.objects.create(
        id="coupon-test-amount-off-forever",
        amount_off=10,
        currency="usd",
        duration="forever",
    )
    self.assertEqual(coupon.human_readable, "$10.00 USD off forever")
    self.assertEqual(str(coupon), coupon.human_readable)