chromium/third_party/blink/web_tests/external/wpt/shadow-dom/focus/focus-click-on-shadow-host.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>HTML Test: click on shadow host with delegatesFocus</title>
<link rel="author" href="mailto:[email protected]">
<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1327136">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>

<body>
  <div id="host"></div>
</body>

<script>
const host = document.getElementById("host");

const shadowRoot = host.attachShadow({ mode: "open", delegatesFocus: true });
// Add an unfocusable spacer, because test_driver.click will click on the
// center point of #host, and we don't want the click to land on focusableDiv
const spacer = document.createElement("div");
spacer.style = "height: 1000px;";
shadowRoot.appendChild(spacer);

const focusableDiv = document.createElement("div");
focusableDiv.tabIndex = 0;
shadowRoot.appendChild(focusableDiv);

promise_test(async () => {
  assert_equals(document.activeElement, document.body);
  // Mouse click
  await test_driver.click(host);
  assert_equals(document.activeElement, host);
  assert_equals(shadowRoot.activeElement, focusableDiv);
  assert_true(host.matches(':focus'));
  assert_true(focusableDiv.matches(':focus'));
  assert_false(focusableDiv.matches(':focus-visible'));
}, ":focus should be applied to the host and the child node when the focus is moved by mouse click");

</script>