chromium/third_party/blink/web_tests/printing/vertical-rl.html

<!DOCTYPE html>
<script>
  if (window.testRunner)
      testRunner.setPrinting();
  if (window.internals)
      internals.settings.setShouldPrintBackgrounds(true);
</script>
<style>
  html { writing-mode: vertical-rl; }
  body { margin:20px; }
</style>
<!-- Note: This test assumes that the page width is more than 600px and less
     than 1200px. There's currently no way of specifying the page size for
     tests.  -->
<div style="writing-mode:horizontal-tb; position:absolute; left:0; top:0; width:200px;">
  <div style="padding-left:10px;">
    There should be a right-aligned blue box on the first page, and a
    right-aligned hotpink box on the second page.
  </div>
</div>
<div style="width:600px; height:100px; break-inside:avoid; background:blue;"></div>
<div style="width:600px; height:100px; break-inside:avoid; background:hotpink;"></div>