Unimproved land but has a septic system

We are looking at a piece of property that is unapproved but it has a septic system if that was installed approximately 10 years ago. As far as I can tell it was fully engineered and permitted with the county and tested. We were able to access the documents at the county office.

However the system has been dormant for 10 years.

What are the odds of this is still a viable system?

Unfortunately, with no water to the property I don't think it's possible to fully test it. Would you have to bring water to the property to test it?