chromium/third_party/blink/web_tests/fast/forms/textarea/textarea-selection-selectAll.html

<!doctype html>
<meta charset=utf-8>
<title>This test selectAll in textarea.</title>
<link rel="author" title="yu.han" href="mailto:[email protected]">
<link rel="help" href="https://html.spec.whatwg.org/multipage/#dom-textarea/input-setselectionrange">
<script src=../../../resources/testharness.js></script>
<script src=../../../resources/testharnessreport.js></script>
<div id=log></div>
<form id="form"><textarea id="form-textarea"></textarea></form>
<script>
test(function() {
    var textarea = document.getElementById('form-textarea');
    textarea.value = 'a\n';
    textarea.focus();
    document.execCommand('selectAll');
    assert_equals(textarea.selectionStart, 0, 'textarea.selectionStart');
    assert_equals(textarea.selectionEnd, 2, 'textarea.selectionEnd');
}, 'textarea selection index is correct when text ends in newline');
</script>