Function verify_mutation 

pub fn verify_mutation(
    preimage: &[u8],
    readback: &[u8],
    matches: &[Match],
    old_bytes: &[u8],
    new_bytes: &[u8],
) -> Verification

Check a readback against the mutation receipt, independently of how the new text was computed: every matched preimage region held exactly the old bytes, every other preimage byte is unchanged and in place, every replaced region holds exactly the new bytes, and nothing else was added.