+
+my $undef = undef;
+is(xml_escape($undef), '', 'xml_escape() returns empty string on undef input');
+my $str = q{'"&<>'};
+is(xml_escape($str), ''"&<>'', 'xml_escape() works as expected');
+is($str, q{'"&<>'}, '... and does not change input in place');
+
+is(C4::Koha::_isbn_cleanup('0-590-35340-3'), '0590353403', '_isbn_cleanup removes hyphens');
+is(C4::Koha::_isbn_cleanup('0590353403 (pbk.)'), '0590353403', '_isbn_cleanup removes parenthetical');
+is(C4::Koha::_isbn_cleanup('978-0-321-49694-2'), '0321496949', '_isbn_cleanup converts ISBN-13 to ISBN-10');
+
+