css/css-contain/contain-layout-016.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Containment Test: Layout containment stacking context</title>
<link rel="author" title="Manuel Rego Casasnovas" href="mailto:rego@igalia.com">
<link rel="help" href="https://drafts.csswg.org/css-contain-1/#containment-layout">
<link rel="match" href="../reference/pass_if_pass_below.html">
<meta name=assert content="Layout containment elements create a stacking context.">
<style>
div {
  contain: layout;
  background: white;
}
span {
  position: relative;
  z-index: -1;
}
</style>

<p>Test passes if there is the word "PASS" below.</p>
<div><span>PASS</span></div>