chromium/third_party/blink/web_tests/external/wpt/css/css-contain/contain-style-counters-001.html

<!DOCTYPE html>

  <meta charset="UTF-8">

  <title>CSS Containment Test: 'contain: style' and counter</title>

  <link rel="help" href="https://www.w3.org/TR/css-contain-1/#containment-style">
  <link rel="match" href="reference/contain-style-counters-001-ref.html">

  <meta content="This test checks that when an element has 'contain: style', then counters which may be affecting its subtree are reset to 0 for such scope." name="assert">

  <style>
  div#create-counter
    {
      counter-reset: counter-of-span 9;
    }

    /*
    This creates a new counter identified as "counter-of-span"
    and initially sets such counter to 9 (an entirely
    arbitrary number).
    */

  div#test
    {
      contain: style;
      font-size: 3em;
    }

  div#test span
    {
      counter-increment: counter-of-span 5;
    }

    /*
    This increments the counter identified as "counter-of-span"
    of the step value of 5 (an entirely arbitrary number) each
    and every time there is a <span> descendant within the subtree
    of div#test
    */

  div#test span::after
    {
      content: counter(counter-of-span);
    }
    /*
    Now, the generated content after the span is set to the
    current value of the counter identified as "counter-of-span"
    */

  </style>


  <p>Test passes if there is the digit 5.

  <div id="create-counter"></div>

  <div id="test"><span></span></div>