css/css-contain/contain-paint-006.html

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

<style>
rbc {
  contain: paint;
  display: ruby-base-container;
  width: 0; /* Because if the test fails, this may get blockified, and which could make wide enough to hold the PASS */
}
rbc::after {
  content: "PASS";
  position: absolute;
}
</style>

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