css/css-contain/contain-size-fieldset-002.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Containment Test: Size containment on fieldset</title>
<link rel="author" title="Vladimir Levin" href="mailto:vmpstr@chromium.org">
<link rel="help" href="https://drafts.csswg.org/css-contain-1/#containment-size">
<link rel="match" href="reference/contain-size-fieldset-002-ref.html">
<meta name=assert content="Size containment does apply to fieldsets, thus their size is the same than if they don't have contents.">
<style>
#border {
  border: 1px solid black;
  width: min-content;
}
fieldset {
  contain: size;
  visibility: hidden;
  height: 1px;
}
</style>

<p>This test passes if it has the same output as the reference. You should see a black border box below.</p>
<div id="border">
  <fieldset>
    <legend>legend</legend>
    Fieldset contents are here.
  </fieldset>
</div>