test(xcatd): cover the noderange ^ file operator

The test runs the real NodeRange code. It sends a ^ range that a
two-argument open would run as a command and checks the command does not
run. It also reads a real comment-only file to show the operator still
works.

The command assertion fails against the previous behavior.

xCAT-test/unit/noderange_file_operator.t

@@ -0,0 +1,51 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use FindBin;
+use File::Spec;
+use File::Temp qw(tempfile);
+use Test::More;
+
+my $libdir = "$FindBin::Bin/../../perl-xCAT";
+plan skip_all => 'NodeRange.pm not found' unless -r "$libdir/xCAT/NodeRange.pm";
+
+# NodeRange requires xCAT::Table at load and creates a nodelist handle once, on
+# entry. Stub Table so the module loads and that init succeeds without a
+# database. The ^file path under test never calls a Table method.
+BEGIN {
+    $INC{'xCAT/Table.pm'} = 1;
+    package xCAT::Table;
+    sub new { return bless {}, shift }
+    sub _set_use_cache { }
+    sub _build_cache   { }
+    our $AUTOLOAD;
+    sub AUTOLOAD { return }
+    sub DESTROY  { }
+}
+eval { require Text::Balanced; 1 } or plan skip_all => 'Text::Balanced is required';
+
+push @INC, $libdir;
+require xCAT::NodeRange;
+
+# The command an injected ^file range would run. The marker must never appear.
+my $marker = File::Spec->catfile(File::Spec->tmpdir, "xcat_nr_marker_$$");
+unlink $marker;
+END { unlink $marker if defined $marker }
+
+# The ^ operator reads node names from a file. A two-argument open would treat
+# the value as a shell pipe and run the command; assert it does not.
+my $evil = '^touch ' . $marker . ' |';
+eval { xCAT::NodeRange::noderange($evil, 0, 0) };
+ok(!-e $marker, 'a piped ^file range does not execute a command');
+
+# A real file that holds only comment and blank lines is opened and read
+# without error and yields no nodes.
+my ($fh, $listfile) = tempfile('xcat_nrlist_XXXXXX', TMPDIR => 1, UNLINK => 1);
+print {$fh} "# a comment line\n\n";
+close $fh;
+my @res = eval { xCAT::NodeRange::noderange('^' . $listfile, 0, 0) };
+is($@, '', 'a real ^file is read without error');
+is_deeply(\@res, [], 'a comment-only ^file yields no nodes');
+
+done_testing();