public async Task CreateCardTokenTest()
        {
            // Arrange
            var args = new CardTokenCreateArguments();

            _stripe.Post(
                Arg.Is <StripeRequest <CardTokenCreateArguments, Token> >(a => a.UrlPath == "tokens" && a.Model == args),
                _cancellationToken).Returns(Task.FromResult(new StripeResponse <Token>()));

            // Act
            var response = await _client.CreateCardToken(args, _cancellationToken);

            // Assert
            response.Should().NotBeNull();
        }