LayoutTests/editing/pasteboard/unrendered-br.html

<script>
if (window.layoutTestController)
     layoutTestController.dumpEditingCallbacks();
</script>
<p>This is a test to make sure that an unrendered br at the end of the selection being pasted into doesn't become rendered as a result of the paste.</p>
<div id="test" contenteditable="true">First&nbsp;<br></div>

<script>
var s = window.getSelection();
var e = document.getElementById("test");

s.setPosition(e, 0);
s.modify("move", "forward", "line");
document.execCommand("InsertHTML", false, "paragraph.<div>Second paragraph.</div>");
</script>