LayoutTests/fast/history/resources/page-cache-helper.html

This page should go back. If a test outputs the contents of this
page, then the test page failed to enter the page cache.
<script>
  function triggerBackNavigation() {
      setTimeout(function() {
          history.back();
      }, 0);
  }

  window.addEventListener("pageshow", (event) => {
      if (event.persisted)
          triggerBackNavigation();
  });

  window.addEventListener("load", function() {
      triggerBackNavigation();
  });
</script>