chromium/third_party/blink/web_tests/external/wpt/dom/nodes/getElementsByClassName-empty-set.html

<!DOCTYPE html>
<html>
<meta charset="utf-8">
<title>Node.prototype.getElementsByClassName with no real class names</title>
<link rel=help href="https://dom.spec.whatwg.org/#dom-document-getelementsbyclassname">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<span class=" ">test</span>

<script>
"use strict";

test(() => {
  const elements = document.getElementsByClassName("");
  assert_array_equals(elements, []);
}, "Passing an empty string to getElementsByClassName should return an empty HTMLCollection");

test(() => {
  const elements = document.getElementsByClassName(" ");
  assert_array_equals(elements, []);
}, "Passing a space to getElementsByClassName should return an empty HTMLCollection");

test(() => {
  const elements = document.getElementsByClassName("   ");
  assert_array_equals(elements, []);
}, "Passing three spaces to getElementsByClassName should return an empty HTMLCollection");

</script>