<!DOCTYPE html>
<html>
<head>
<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
<meta name="assert" content=":focus should match a shadow host which contains the focused element">
<link rel="help" href="https://html.spec.whatwg.org/#element-has-the-focus">
</head>
<body>
<p>Test passes if you see a single 100px by 100px green box below.</p>
<div id="host"></div>
<style>
#host { background: red; width: 100px; height: 100px; }
#host:focus { background: green; }
</style>
<script>

const shadowRoot = host.attachShadow({mode: 'closed'});
shadowRoot.innerHTML = '<div tabindex="0" style="outline: none;"></div>';
shadowRoot.firstChild.focus();

</script>
</body>
</html>