chromium/third_party/blink/renderer/core/testing/data/select_range_iframe.html

<!DOCTYPE html>
<html>
<body>
This is a test case for selecting a range within an iframe.
<iframe id='target' width='400' height='200' src='select_range_basic.html'></iframe>
<script>
    document.getElementById('target').contentWindow.focus();
</script>
</body>
</html>