Taking checkpoint (Snapsure) in secondary VNX File (MirrorView Protected)

We are having two VNX File (NAS) that is connecting by MirrorView/S. It is an Active/Standby cluster. What we want to do is mount the secondary box image and do the read/write test. After that we can do a full sync from primary box if required (i.e. discard the change in secondary box). Our bottom line is keeping the primary box untouched as it runs production systems. It's simple to take snapshot in secondary/DR in VNX Block or VMAX and then mount the snapshot for testing. But somehow from what I were told, that's not the same case for VNX File.

I find that there is a feature called Snapsure and looks like it can create read/writable checkpoint in secondary box. Have anyone tried to take read/writable checkpoint in secondary VNX File that is protected by MirrorView/S?

Appreciate for your comments!!