[...] Test::HTTP::LocalServer [...] substitute the base URI for accessing the modem to be a file:// URI instead.

T:HTTP::LocalServer seems to pretty much mirror what I'm doing. With a bit less hardcoded single-purpose, anyway.

I don't like the idea of going file:/// though, since that means I'd have to add an extra magic hook in the code to say "here, use this fake URL instead", which would defeat a lot of the purpose of running through the code path in the first place. It would still run the LWP bits, but the URL construction would be bypassed. Also doesn't give it the chance to double check that it properly errors on 404 as the test currently does either.