How can I validate WOPI is working on OOS on-prem using PowerShell or REST?

Question

I'm trying to trouble shoot our on-prem OOS and read about the WopiTest framework for Office 365 at MS Docs - WOPI Validation application

Does Office Online Server have a corresponding framework for validating the WOPI framework?
(I couldn't find any REST calls at https://officeonline-onprem/hosting/discovery)

In that case, how can this be done using PowerShell Invoke-RestMethod?

I do have a method to call OOS WOPI-rendering using PowerShell Invoke-WebRequest, but since iFrames isn't exposed, I can't tell if rendering was performed or not.
(Well, if I use another tool and sniff the answer I can get the iFrame URL:s returned. But that seems a bit overkill.)

Answer 1

Well, if I use another tool and sniff the answer I can get the iFrame URL:s returned. But that seems a bit overkill.

I am afraid that's the only way to do it with the on-prem OOS as it doesn't expose any testing URLs such as the cloud version does.