It seems very clear and easy to use, well done! I am wondering if there is any test environment like with Stripe in order to validate the flow in development?
The test cases for this library validate against the XSD for the ISO files, which could be extended to handle more test cases.
Banks sometimes offer a test SFTP endpoint they use. Engineers have had to do this from scratch at the companies they worked at in the past. If this is something you're interested in, we should talk more @ svapnil@woodside.sh