I don't know how feasible this is, but one idea I've toyed with is doing all the installation and configuration except for the last steps (whatever steps you are testing) on a VM machine, then making an installable image of that machine and installing it onto the real hardware for the final work. It should be bit-for-bit identical to an install done directly onto the hardware, as far as I can work out.

Then do your final installation and testing.

If anything goes wrong with the configuration, you presumably will have been smart enough to have done snapshots along the way of your VMs (at various steps during the preparation) and you can just roll back to any snapshot if you need to, then fix things and push it back onto the metal.

Only problem with this is that I haven't actually done it, so I don't know for a fact that it works. It just seems like it should work.