css/css-contain/contain-layout-003.html

<!doctype html>
<html lang=en>
  <meta charset=utf-8>
  <title>CSS-contain test: layout containment on ruby-base-container</title>
  <link rel="author" title="Florian Rivoal" href="https://florian.rivoal.net">
  <meta name=flags content="ahem">
  <meta name=assert content="layout containment does not apply to ruby-base-container">
  <link rel="match" href="../reference/ref-filled-green-100px-square.xht">
  <link rel=help href="https://drafts.csswg.org/css-contain-1/#containment-layout">

<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
<style>
div {
  position: relative;
  background: red;
  width: 100px;
  height: 100px;
  padding: 25px;
  box-sizing: border-box;
}
rbc {
  contain: layout;
  display: ruby-base-container;
  font-family: Ahem;
  font-size: 100px;
  line-height: 1;
}
rbc::after {
  content: "X";
  color: green;
  position: absolute;
  top:0; left: 0;
}
</style>

<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
<div><ruby><rbc></rbc></ruby></div>