def METHOD_NAME(self):
    first_value = 'https://op'
    second_value = ['https://client.com.br/oidc_callback']
    self.client.post(url_for('register'), json={
        'op_url': first_value,
        'redirect_uris': second_value
    })
    ClientHandler.__init__.assert_called_once_with(first_value, second_value, {})