custom-highlight-painting-overlapping-highlights-001.html

<!DOCTYPE html>
<meta charset="UTF-8">
<title>CSS Highlight API Test: Overlapping Highlights</title>
<link rel="help" href="https://drafts.csswg.org/css-highlight-api-1/">
<link rel="match" href="custom-highlight-painting-overlapping-highlights-001-ref.html">
<meta name="assert" value="UAs must not define any styles for custom highlight pseudo-elements in the default UA stylesheet.">
<style>
  body {
    font-size: 3em;
    font-weight: bolder;
  }
  #affected1::highlight(highlight1) {
    color: red;
  }
  #affected2::highlight(highlight2) {
    color: green;
  }
</style>
<body><span id="affected1">This should have 'highlight1' style (red).</span><span id="affected2">This should have 'highlight2' style (green).</span>
<script>
  /*
    This test is meant to verify that:
      - UAs must not define any styles for custom highlight pseudo-elements in
      the default UA stylesheet.
      - UAs do not paint unstyled custom highlights.

    In this test, highlight2 has higher priority because it was registered
    later, so it is painted over highlight1. This includes painting for
    span#affected1, where there is no CSS rule for highlight2. But since unstyled
    custom highlights are not painted, span#affected1 is still painted with the
    styles for highlight1.

    See https://drafts.csswg.org/css-highlight-api-1/#default-styles
  */

  const node = document.body;
  let r = new Range();
  r.setStart(node, 0);
  r.setEnd(node, 2);

  CSS.highlights.set("highlight1", new Highlight(r));
  CSS.highlights.set("highlight2", new Highlight(r));
</script>

chromium/third_party/blink/web_tests/external/wpt/css/css-highlight-api/painting/custom-highlight-painting-overlapping-highlights-001.html