How to create sub account on Testnet

I’m trying to create sub account from my master account via Testnet endpoints. However, it’s always show a web page Something bad happened :(.
I understand that the sub-account features only support the Corporate Account type, but I do not know how to accomplish that in the Testnet.

–> How can I create sub-accounts and make a sample about: funding, tranfer, withdraw,… among them?

(I’ve set up the correct HMAC API key)

Hi. Sorry about it, currently sub-account related features are not provided in testnet.

How I do to test sub-accounts?