RBAC testing - What does it actually do?

I am a developer, I understand what RBAC means, to give a simple example

It is USER -> ROLES -> RIGHTS

(i.e) A user can have any number of roles (internal permission for each modules) then based on that consolidated value of permissions then user will be given with the privilege

But my client what us to look at RBAC testing, What does it mean? Does it mean like I need to create different users with different set of roles and test their functionality?

Any help is appreciated.

Thanks,
Harry