Is there any way to test IBM Cloud Storage offline/on my local system?
For AWS S3 there are plenty of libraries like the following:
This way i can play around with the API without the fear that i could potentially cause a thousand dollar bill.
Is there something like this for IBM COS?
There is a "Lite plan" which is free:
"Lite plan instance is free to use for Storage capacity up to 25 GB per month. Lite plan instance is used for trial, and can be easily upgraded to Standard plan for unlimited scalability and full functionality."
So although I'm not aware of any local options, this one should allow you to test without fear of cost.