chromium/third_party/blink/web_tests/external/wpt/css/selectors/is-where-pseudo-elements-ref.html

<!DOCTYPE html>
<title>:is() combined with pseudo elements</title>
<link rel="help" href="https://drafts.csswg.org/selectors-4/#matches">
<style>
  #b::before, #d::before {
    content: "before ";
    color: green;
  }
  #e::after, #h::after {
    content: " after";
    color: green;
  }
  #a::first-letter, #b::first-letter {
    color: blue;
  }
  #g::first-line, #l::first-line {
    color: magenta;
  }
</style>
<main id=main>
  <div id=a>a</div>
  <div id=b>b</div>
  <div id=c>c</div>
  <div id=d>d</div>
  <div id=e>e</div>
  <div id=f>f</div>
  <div id=g>g</div>
  <div id=h>h</div>
  <div id=j>j</div>
  <div id=k>k</div>
  <div id=l>l<br>l2</div>
</main>