chromium/third_party/blink/web_tests/editing/selection/extend-inside-transforms-forward.html

<!doctype html>
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<script src="../assert_selection.js"></script>
<script src="../../resources/ahem.js"></script>
<script>
selection_test(
  [ '<div contenteditable style="transform: rotate(-45deg); font:10px Ahem;">',
    '<p>he|llo</p><p>world</p></div>' ],
  selection => selection.modify('extend', 'forward', 'line'),
  [ '<div contenteditable style="transform: rotate(-45deg); font:10px Ahem;">',
    '<p>he^llo</p><p>wo|rld</p></div>' ],
  ' ensures extending forward line vertically inside transform: rotate');

selection_test(
  [ '<div contenteditable style="transform: rotate(-45deg); font:10px Ahem;">',
    '<p>hello</p><p>wo|rld</p></div>' ],
  selection => selection.modify('extend', 'backward', 'line'),
  [ '<div contenteditable style="transform: rotate(-45deg); font:10px Ahem;">',
    '<p>he|llo</p><p>wo^rld</p></div>' ],
  ' ensures extending backward line vertically inside transform: rotate');
</script>