The unit I received was not thoroughly tested. It was a MDM (Mobile device management). This means whoever had it registered it with Apple with their corporation. This is similar to iCloud lock, but instead when you wipe the disk and go to install OS (even on another hard drive) the SN will ping you Apples servers and require you to install profiles that align with the corporations parameters.What disappointed me the most is that this was “renewed” and allegedly tested. Failure to take the extra 20 seconds to do this advises that this seller was about profits over people.While I did get a refund the experience alone is a huge turn off. Buyer beware.