[zbentley]

Possible, yes, but certainly not easier—especially not if the test harness doesn’t manage filesystems anywhere else.

And even then, that’s still a behavior mock, of a kind. There are lots of ways in which a dummy ISO mount behaves much unlike filesystems your deployed code might run on. You could address those issues, but doing so is very laborious and starts requiring more and more specialized code. Unless the code under test is part of a database storage engine or something, it’s likely even less worth it.