This commit adds a tests/xml directory, and an LD_PRELOAD module which
can fake arbitrary libvirt XML from an external file (and is therefore
a much more flexible test than using the libvirt test:// driver
alone).
Also added is one regression test for:
https://bugzilla.redhat.com/show_bug.cgi?id=701814
Loading the given libvirt XML using Sys::Guestfs::Lib::open_guest
used to fail with the error:
format parameter is empty or contains disallowed characters at /home/rjones/d/libguestfs/perl/blib/lib/Sys/Guestfs/Lib.pm line 256.
Thanks to Tom Horsley for supplying the test data.