chromium/chrome/test/data/chromeos/virtual_keyboard/default_extension/end_to_end_test.html

<!--
Copyright 2013 The Chromium Authors
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->
<html>
<head>
  <title>Check whether the Virtual Keyboard works</title>
</head>
<body>
  <input id='input' type='text'/>
</body>
<script>
  var success = false;
  var input = document.getElementById('input');
  input.oninput = function() {
    success = true;
  };
  input.focus();

  var verifyInput = function(expected) {
    return input.value == expected;
  };

  var waitForInput = function(char) {
    return new Promise(resolve => {
      input.oninput = function() {
        resolve(verifyInput(char));
      };
    });
  };
</script>
</html>