I unfortunately don't see any pre-SureBackup job scripts, but even so that wouldn't be a helpful script until the VM is already registered as a minimum.
As Mike said, the test script will be injected and executed inside the VM, which is unable to boot. I don't see any creative ways of automating this.
Could a workaround be to encrypt, via Bitlocker, the VHDX files host-side instead of in-guest?
Principal Technologist, Global Education Services @ Veeam Software
Veeam Certified Architect #1 | Veeam Certified Trainer #4 [v7,v8,v9] | Veeam Certified Trainer Mentor #1