chromium/third_party/blink/web_tests/external/wpt/css/css-multicol/multicol-rule-nested-balancing-001.html

<!DOCTYPE html>
<html>
  <meta charset="utf-8">
  <title>CSS Multi-column Layout Test: Test the column rules' block-size with nested balancing multicol container</title>
  <link rel="author" title="Ting-Yu Lin" href="mailto:[email protected]">
  <link rel="author" title="Mozilla" href="https://www.mozilla.org/">
  <link rel="help" href="https://drafts.csswg.org/css-multicol-1/#cf">
  <link rel="help" href="https://drafts.csswg.org/css-multicol-1/#column-gaps-and-rules">
  <link rel="help" href="https://github.com/w3c/csswg-drafts/issues/2309">
  <link rel="match" href="multicol-rule-nested-balancing-001-ref.html">
  <meta name="assert" content="This test verifies that the column-rules are extended to the content block-end edges of their corresponding inner and outer multicol container.">

  <style>
  .outer {
    column-count: 2;
    column-rule: 6px solid black;
    width: 400px;
    height: 250px;
  }
  .inner {
    column-count: 2;
    column-rule: 3px solid gray;
    height: 200px;
  }
  .outer-block {
    background-color: lightgreen;
    height: 200px;
  }
  .inner-block {
    background-color: lightblue;
    height: 300px;
  }
  </style>

  <article class="outer">
    <div class="outer-block"></div>
    <article class="inner">
      <div class="inner-block"></div>
    </article>
  </article>
</html>