<!DOCTYPE html>
<html>
<head>
<style>
my-host {
  display: block;
  width: 100px;
  height: 25px;
  background: red;
}
</style>
</head>
<body>
<p>Test passes if you see a single 100px by 100px green box below.</p>
<my-host id="t1"></my-host>
<my-host id="t2" class="match"></my-host>
<my-host id="t3" class="no-match"></my-host>
<my-host id="t4" class="match"><div></div></my-host>

<script>
var host = document.querySelector('#t1');
host.attachShadow({ mode: 'open' }).innerHTML = `
  <style>
    :host > div {
      background-color: green; width: 100%; height: 100%;
    }
  </style>
  <div></div>
`;

var host = document.querySelector('#t2');
host.attachShadow({ mode: 'open' }).innerHTML = `
  <style>
    div { background-color: red; width: 100%; height: 100%; }
    :host(.match) .descendant {
      background-color: green;
    }
  </style>
  <div><div class="descendant"></div></div>
`;

var host = document.querySelector('#t3');
host.attachShadow({ mode: 'open' }).innerHTML = `
  <style>
    div { background-color: green; width: 100%; height: 100%; }
    :host(.match) div {
      background-color: red;
    }
  </style>
  <div></div>
`;

var host = document.querySelector('#t4');
host.attachShadow({ mode: 'open' }).innerHTML = `
  <style>
    :host(.match) ::slotted(div) {
      background-color: green; width: 100%; height: 100%;
    }
  </style>
  <slot></slot>
`;

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