textarea-insertfrompaste-type-inputevent-data.html

<!DOCTYPE html>
<html>
<body>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<textarea id="text">Copying and pasting some part of the text should set
  the event.data with the selected part for inputType insertFromPaste</textarea>
<script>
  const text = document.getElementById("text");
  let eventData;
  text.addEventListener('input', (evt) => {
    if(evt.inputType == 'insertFromPaste')
      eventData = evt.data;
  });
  test(function () {
    text.focus();
    // Selecting first word of the text.
    text.setSelectionRange(0, 7);
    const selectedData = getSelection().toString();
    // Copy and paste should fire input event with inputType insertFromPaste.
    document.execCommand("copy");
    document.execCommand("paste");
    // Event data should now be set with the first word of the text
    // which is "Copying".
    assert_equals(selectedData, "Copying");
    assert_equals(eventData, selectedData);
  }, 'Input event data for inputType insertFromPaste should be set');
</script>
</body>
</html>

chromium/third_party/blink/web_tests/external/wpt/input-events/textarea-insertfrompaste-type-inputevent-data.html