def METHOD_NAME(self):
    self.data['client_id'] += '_confidential'
    self.oauth_client = self.create_confidential_client(self.user, self.data['client_id'])
    self._assert_error(  # lint-amnesty, pylint: disable=no-value-for-parameter
        self.data,
        "invalid_client",
        f"{self.client_id}_confidential is not a public client",
    )