css/cssom/selectorText-modification-restyle-002.html

<!DOCTYPE html>
<title>CSSOM: Modify selectorText in a shadow tree stylesheet</title>
<link rel="author" title="Rune Lillesveen" href="mailto:futhark@chromium.org">
<link rel="help" href="https://drafts.csswg.org/cssom/#dom-cssstylerule-selectortext">
<link rel="help" href="https://drafts.csswg.org/css-scoping/#selectors">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  #container { color: red }
  .subtree * { color: pink }
</style>
<div id="container">
  <div id="host"></div>
</div>
<script>
  const root = host.attachShadow({mode:"open"});
  root.innerHTML = "<style>nomatch { color: green }</style><div>Green</div>";
  const div = root.querySelector("div");

  test(() => {
    assert_equals(getComputedStyle(div).color, "rgb(255, 0, 0)", "Color should initial be red.");
  }, "Check initial color.");

  test(() => {
    // The combination of the .subtree and CSSOM selector style invalidations
    // caused the Blink implementation to fail an assertion.
    container.className = "subtree";
    root.styleSheets[0].cssRules[0].selectorText = "div";
    assert_equals(getComputedStyle(div).color, "rgb(0, 128, 0)", "Color should be green after stylesheet change.");
  }, "Check that color changes correctly after shadow stylesheet selector and #container class is changed.");
</script>