chromium/third_party/blink/web_tests/accessibility/scroll-div-horiz-sends-notification.html

<!DOCTYPE HTML>
<html>
<head>
  <script src="../resources/testharness.js"></script>
  <script src="../resources/testharnessreport.js"></script>
<style>
.container {
  padding: 100px;
  margin: 100px;
  border: 1px solid #000;
  height: 900px;
  overflow: scroll;
}
.inner {
  width: 2000px;
}
.bigbutton {
  display:inline-block;
  width: 600px;
  height: 600px;
}
</style>
</head>
<body>

<div id="container" class="container">
    <div class="inner">
        <button class="bigbutton">One</button>
        <button class="bigbutton">Two</button>
        <button class="bigbutton">Three</button>
    </div>
</div>

<script>

async_test((t) => {
  var container = document.getElementById('container');

  accessibilityController.addNotificationListener(t.step_func((target, notification) => {
    if (target.role == 'AXRole: AXGenericContainer') {
      console.log('Got notification on container div');
      assert_equals(container.scrollLeft, 500);
      t.done();
    }
  }));

  window.setTimeout(function() {
    container.scrollLeft = 500;
  }, 0);

  window.setTimeout(t.step_func_done(() => {
    assert_unreached();
  }), 200);
}, "This test ensures that scrolling the window sends a notification.");

</script>

</body>
</html>