selection/extend-selection-in-shadow-tree.html

<!doctype HTML>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-actions.js"></script>
<script src="/resources/testdriver-vendor.js"></script>
<div id="div1">
  <template shadowrootmode="open">
    <div id="div2">some text</div>
  </template>
</div>
<script>
  const selection = document.getSelection();
  const div1 = document.getElementById("div1");
  const div2 = div1.shadowRoot.getElementById("div2");
  generateShadowRootClickSequence = () => new test_driver.Actions()
    .pointerMove(div2.offsetLeft, div2.offsetTop)
    .pointerDown()
    .pointerUp()

  promise_test(async () => {
    await generateShadowRootClickSequence().send();
    selection.extend(div2.firstChild, 9); // select "some text"
    assert_equals(selection.toString(), "some text");
  }, 'Extend selection in shadow tree');
</script>