+
+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');
+
+is(C4::Koha::NormalizeISBN({ isbn => '978-0-321-49694-2 (pbk.)', format => 'ISBN-10', strip_hyphens => 1 }), '0321496949', 'Test NormalizeISBN with all features enabled' );
+
+my @isbns = qw/ 978-0-321-49694-2 0-321-49694-9 978-0-321-49694-2 0321496949 9780321496942/;
+is( join('|', @isbns), join('|', GetVariationsOfISBN('978-0-321-49694-2 (pbk.)')), 'GetVariationsOfISBN returns all variations' );
+
+is( join('|', @isbns), join('|', GetVariationsOfISBNs('978-0-321-49694-2 (pbk.)')), 'GetVariationsOfISBNs returns all variations' );
+
+my $isbn;
+eval {
+ $isbn = C4::Koha::NormalizeISBN({ isbn => '0788893777 (2 DVD 45th ed)', format => 'ISBN-10', strip_hyphens => 1 });
+};
+ok($@ eq '', 'NormalizeISBN does not throw exception when parsing invalid ISBN (bug 12243)');
+
+@isbns = GetVariationsOfISBNs('abc');
+is(scalar(@isbns), 0, 'zero variations returned of invalid ISBN');