LayoutTests/fast/forms/input-text-enter.html

<p>This test selects some characters, then simulates a press of the Enter key (marked Return on Macintosh keyboards).</p>
<p><input id="input" value="12345678"></input></p>
<p>Content of input after pressing return is "<span id="result"></span>". It should be "12345678".</p>
<script>
if (window.testRunner)
    testRunner.dumpAsText();
var input = document.getElementById("input");
input.setSelectionRange(2, 6);
var event = document.createEvent("KeyboardEvents");
event.initKeyboardEvent("keypress", true, true, document.defaultView, "Enter", 0, false, false, false, false, false);
input.dispatchEvent(event);
if (window.eventSender)
    eventSender.keyDown('\n', []);
document.getElementById("result").innerText = input.value;
</script>