chromium/third_party/blink/web_tests/external/wpt/selection/contenteditable/collapse.html

<!DOCTYPE HTML>
<meta charset=utf-8>
<title>Selection across multiple contenteditable</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<button id="button"></button>
<div contenteditable id="host1"></div>
<div contenteditable id="host2"></div>
<div contenteditable id="host3">
  <div contenteditable="false">
    <div contenteditable id="host4"></div>
  </div>
</div>
<script>
function clearFocus() {
  // Move focus from editable host to a button to remove selection limiter
  button.focus();
}
test(() => {
  clearFocus();
  getSelection().collapse(host1);
  assert_equals(document.activeElement, host1);
  getSelection().collapse(host2);
  assert_equals(document.activeElement, host2);
}, "Selection.collapse() must succeed across siblings");

test(() => {
  clearFocus();
  getSelection().collapse(host4);
  assert_equals(document.activeElement, host4);
  getSelection().collapse(host3);
  assert_equals(document.activeElement, host3);
}, "Selection.collapse() must succeed for the ancestor");


test(() => {
  clearFocus();
  getSelection().collapse(host3);
  assert_equals(document.activeElement, host3);
  getSelection().collapse(host4);
  assert_equals(document.activeElement, host4);
}, "Selection.collapse() must succeed for the descendant");
</script>