<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS test reference</title>
<link rel="author" title="Florian Rivoal" href="https://florian.rivoal.net/">
<style>
div { white-space: pre; }
span {
  background: blue;

  /* to make the span go under the right border */
  z-index:-1;
  position: relative;
}
aside {
  display: inline-block;
  width: 0.5em;
  border-right: 1em white solid;
}
</style>

<p>Test passes if the characters below are arranged in a square and if there is a blue rectangle at the end of the first line.
<div>ああ<aside><span>&#x3000;</span></aside><br>ああ</div>
