<body onload="test()">
Try to select this text.<br>Pass if non-selection is visible.
<pre id=result_with_default_prevent></pre>
<pre id=result_without_default_prevent></pre>
</body>
<script>

function mousemoveFunction(event) {
  event.preventDefault();
}

document.body.onmousemove = mousemoveFunction;

function test() {
  if (window.testRunner)
    testRunner.dumpAsText();
  if (!window.eventSender)
    return;

  eventSender.mouseMoveTo(0, 0);
  eventSender.mouseDown();
  eventSender.mouseMoveTo(400, 400);
  eventSender.mouseUp();

  result_with_default_prevent.innerHTML = window.getSelection();

  document.body.onmousemove = "";

  eventSender.mouseMoveTo(0, 0);
  eventSender.mouseDown();
  eventSender.mouseMoveTo(400, 400);
  eventSender.mouseUp();
 
  result_without_default_prevent.innerHTML = window.getSelection();
}
</script>