css/css-contain/contain-layout-baseline-001.html

<!doctype html>
<html lang=en>
  <meta charset=utf-8>
  <title>CSS-contain test: layout containment and baselines</title>
  <link rel="author" title="Florian Rivoal" href="https://florian.rivoal.net">
  <meta name=assert content="With contain:layout, for the purpose of the vertical-align property, the containing element is treated as having no baseline.">
  <link rel="match" href="../reference/ref-filled-green-100px-square.xht">
  <link rel=help href="https://drafts.csswg.org/css-contain-1/#containment-layout">

<style>
#red {
  position: absolute;
  background: red;
  width: 100px;
  height: 100px;
  z-index: -1;
}
.green {
  display: inline-block;
  height: 100px;
  background: green;
  width: 50px;
  contain: layout;
  color: transparent;
}
</style>

<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
<div id=red></div>
<div class=green></div><div class=green>a</div>