chromium/third_party/blink/web_tests/external/wpt/editing/run/caret-navigation-after-removing-line-break.html

<!DOCTYPE HTML>
<style>
    .wrap span {
        white-space: pre-wrap;
    }
</style>
<div class="wrap">
    <span id="initial" contenteditable="true"> abcd </span>111<span id="before" contenteditable="true"> efgh </span>222<br><span id="after" contenteditable="true"> ijkl </span>333<span id="next" contenteditable="true"> mnop </span>444<span id="last" contenteditable="true"> qrst </span>
</div>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>
<script src="/resources/testdriver-actions.js"></script>
<script>
const KEY_CODE_MAP = {
  'ArrowLeft':  '\uE012',
  'ArrowUp':    '\uE013',
  'ArrowRight': '\uE014',
  'ArrowDown':  '\uE015',
  'Tab': '\uE004',
  'S': '\u0053',
};

function keyPress(target, key) {
  const code = KEY_CODE_MAP[key];
  return test_driver.send_keys(target, code);
}

function deletebr() {
  let el;
  el = document.querySelector('br');
  if (el) {
    el.remove();
  }
}

// Delete the <br> element so that we get a single line
deletebr();

const s = getSelection();
promise_test(async t => {
  initial.focus();
  let node = initial.firstChild;
  assert_equals(s.anchorNode, node, "Focus must be at the span with 'abcd'");
  assert_equals(s.anchorOffset, 0, "Caret must be at the start of the 'abcd' text");

  await keyPress(initial, "Tab");
  node = before.firstChild
  assert_equals(s.anchorNode, node, "Caret moved to span with 'efgh'");
  assert_equals(s.anchorOffset, 0, "Caret must be at the start of the 'efgh' text");

  await keyPress(before, "Tab");
  node = after.firstChild
  assert_equals(s.anchorNode, node, "Focus must be at the span with 'ijkl'");
  assert_equals(s.anchorOffset, 0, "Caret must be at the start of the 'efgh' text");

  await keyPress(after, "Tab");
  node = next.firstChild
  assert_equals(s.anchorNode, node, "Focus must be at the span with 'mnop'");
  assert_equals(s.anchorOffset, 0, "Caret must be at the start of the 'efgh' text");

}, "Navigate after deleting <br>");

promise_test(async t => {
  initial.focus();
  await keyPress(initial, "Tab");
  await keyPress(before, "Tab");
  await keyPress(after, "Tab");
  await keyPress(next, "ArrowRight");
  await keyPress(next, "ArrowRight");
  await keyPress(next, "ArrowRight");

  await keyPress(next, "S");
  assert_equals(next.firstChild.textContent, " mnSop ", "Inserting a 'S' char betwen 'n' and 'o'");
}, "Insert text after deleting <br>")

</script>