assertEquals(0, tags.length);

        // Test mixed whitespace and commas
        tags = PrunedTag.parse(" , , , ");
        assertEquals(0, tags.length);
    }

    public void test_parse_invalidFormats() {
        // Test invalid formats that should throw FessSystemException
        try {
            PrunedTag.parse("invalid_format_with_special_chars@#$%");