chromium/third_party/blink/web_tests/external/wpt/css/selectors/hover-002.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Selectors: Change class to enable :hover</title>
<link rel="author" title="Rune Lillesveen" href="[email protected]">
<link rel="help" href="https://drafts.csswg.org/selectors/#the-hover-pseudo">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-actions.js"></script>
<script src="/resources/testdriver-vendor.js"></script>
<style>
  .affected:hover { color: green }
  #hoveredContents { display: contents }
</style>
<div id="hovered">Hover me - should become green</div>
<div id="hoveredContents">
  <div id="hovered2">Hover me - should become green</div>
</div>
<script>
  function mouseMoveToTarget(selector) {
     let target = document.querySelector(selector);
     return new test_driver.Actions().pointerMove(0, 0, {origin: target})
             .send();
  }

  function testElementGreen(test, element) {
    element.addEventListener("mouseover", test.step_func(event => {
      assert_equals(getComputedStyle(element).color, "rgb(0, 128, 0)");
      test.done();
    }));
  }

  // Setting the affected classes here makes the two elements go from never
  // reacting to hover to being affected by hover without changing computed
  // style.
  hovered.offsetTop;
  hovered.className = "affected";
  hoveredContents.className = "affected";

  async_test(t => { testElementGreen(t, hovered); }, "Hover #hovered element should make it go green");
  async_test(t => { testElementGreen(t, hovered2); }, "Hover #hoveredContents child should make it go green");

  mouseMoveToTarget("#hovered").then(() => {
    mouseMoveToTarget("#hovered2");
  });

</script>