test(probe): cover the discovery download match

The network boot script of the upstream loader and of xNBA, and the
pxelinux configuration, start the discovery. A node script, a loader
and a Genesis file do not.

xCAT-test/unit/probe_utils_discovery_boot_download.t

@@ -0,0 +1,31 @@
+#!/usr/bin/env perl
+# xcatprobe discovery marks the boot loader stage of an unknown node when it fetches its pxelinux
+# configuration or its network boot script. The file names are the ones the TFTP and HTTP logs show.
+use strict;
+use warnings;
+
+use FindBin;
+use lib "$FindBin::Bin/../../perl-xCAT";
+use lib "$FindBin::Bin/../../xCAT-probe/lib/perl";
+
+use Test::More;
+
+require probe_utils;
+
+my @starts = (
+    '/tftpboot/xcat/ipxe/nets/192.0.2.0_24',
+    '/tftpboot/xcat/ipxe/nets/192.0.2.0_24.uefi',
+    '/tftpboot/xcat/xnba/nets/192.0.2.0_24',
+    '/tftpboot/pxelinux.cfg/C0000200',
+);
+ok( probe_utils::discovery_boot_download($_), "$_ starts the discovery" ) for @starts;
+
+my @others = (
+    '/tftpboot/xcat/ipxe/nodes/cn01',
+    '/tftpboot/xcat/ipxe/i386/undionly.kpxe',
+    '/tftpboot/xcat/genesis.kernel.x86_64',
+);
+ok( !probe_utils::discovery_boot_download($_), "$_ does not" ) for @others;
+ok( !probe_utils::discovery_boot_download(undef), 'no file name does not' );
+
+done_testing();