Testing user rights as admin

As an admin I want to test the rights of a dedicated user.

I want to check if things that shouldn’t be viewable or editable for the user is set correctly. How can I do that?

In addition, as we want a wiki with openidconnect login only (it shouldn’t be possible to skip oidc), I won’t have the possibility to create a testuser just for this purpose.

Do you have any ideas?
Regards, Simpel