'Regression test for #10643: the security hash should allow forms with
empty_permitted = True, or forms where data has not changed.'

def test_empty_permitted(self):

    f1 = HashTestBlankForm({})
    f2 = HashTestForm({}, empty_permitted=True)
    hash1 = utils.form_hmac(f1)
    hash2 = utils.form_hmac(f2)
    self.assertEqual(hash1, hash2)
