They are described here: Where is my merchant interface (AlphaHub Portal) located?
I have got an answer from AlphaCommerceHub:
Sandbox is an internal environment that shouldn’t be in the customer facing documentation – I’ll have the team update this.
Test is the environment that your accounts have been setup in, however that is the wrong URL in the documentation for AlphaCommerceHub as well.
Pleases use the below URLS:
For API calls:
UAT: https://hubapiuat.alphacommercehub.com.au
Prod: https://hubapi.alphacommercehub.com.au
For HPP calls:
UAT: https://hubuat.alphacommercehub.com.au/pp/
Prod: https://hub.alphacommercehub.com.au/pp/