chromium/third_party/blink/web_tests/fast/forms/hidden/hidden-value.html

<html>
    <head>
        <script language="javascript">
        function test()
        {
            if (window.testRunner)
                testRunner.dumpAsText();
            
            var frm = document.getElementById("frm");
            var tf = document.getElementById('tf');
            tf.setAttribute('value', 'Almost Original Value');
            tf.value = "New value";
            log('Markup: ' + String(frm.innerHTML));
            log('Value: ' + tf.value);
            log('Attribute: ' + tf.getAttribute('value'));
            frm.reset();
            log('After reset');
            log('Markup: ' + String(frm.innerHTML));
            log('Value: ' + tf.value);
            log('Attribute: ' + tf.getAttribute('value'));
        }

        var console_messages = document.createElement("ol");

        function log(message)
        {
          var console = document.getElementById('console');
          var item = document.createElement("li");
          item.appendChild(document.createTextNode(String(message).replace(/0x[0-9a-fA-F]{8}/g, "0xXXXXXXXX")));
          console.appendChild(item);
        }

        </script>
    </head>
    <body onload="test()">
        This tests that the JS property value and the attribute value for a hidden input field are the same.<br>
        <form id="frm">
                <input type="hidden" id="tf" value="Original value">
        </form>
        <div id="console"></div>
    </body>
</html>