LayoutTests/editing/selection/inactive-selection.html

<p>This test verifies that an editable element in one frame retains an inactive selection
after you've made a selection in another frame.</p>
<hr>
<pre id="console"></pre>

<iframe src="data:text/html, <div id='input' contenteditable='true'>should be an inactive selection</div>"></iframe>
<br>
<input id='input' type="text" value="random text">
<div>
<script>
window.onload = function() {
    if (window.testRunner)
        testRunner.dumpAsText();
        
    var div = frames[0].document.getElementById('input');
    frames[0].getSelection().setBaseAndExtent(div, 0, div, 1);
    frames[0].focus();

    window.focus();
    document.getElementById('input').focus();

    var selectionString = frames[0].getSelection().toString();
    if (div.innerText == selectionString)
        document.getElementById('console').innerHTML = 'PASS: inactive selection retained.';
    else
        document.getElementById('console').innerHTML = 'FAIL: inactive selection should be "' + div.innerText + '" but instead is ' + selectionString  + '.';
}
</script>