chromium/src/third_party/blink/web_tests/fast/spatial-navigation/snav-container-only-white-space.html

<style>
  :focus {outline: 1px solid black;}
</style>

<a href="#" id="start">This is an element</a><br>
<div>
  <a href="#" id="1"></a>
</div>
<div>
  <a href="#" id="2">This is an element</a><br>
</div>

<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<script src="resources/snav-testharness.js"></script>
<script>
  var resultMap = [
    ["Down", "2"],
    ["Up", "start"],
  ];

  // Start at a known place.
  document.getElementById("start").focus();
  snav.assertFocusMoves(resultMap);
</script>