chromium/third_party/blink/web_tests/external/wpt/css/cssom/serialize-all-longhands.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Serialize all longhands</title>
<link rel="author" title="Oriol Brufau" href="mailto:[email protected]" />
<link rel="help" href="https://drafts.csswg.org/cssom/#dom-cssstyledeclaration-getpropertyvalue">
<meta name="assert" content="Checks that all longhands indexed in a CSSStyleDeclaration can be serialized to a non-empty string when set to their initial value.">

<div id="target"></div>

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
function nonSerializableProperties(style) {
  const result = [];
  assert_greater_than(style.length, 0, "Should have longhands");
  for (let property of style) {
    if (!style.getPropertyValue(property)) {
      result.push(property);
    }
  }
  return result;
}

const target = document.getElementById("target");
target.style.cssText = "all: initial; direction: initial; unicode-bidi: initial;";

test(function() {
  const props = nonSerializableProperties(target.style);
  assert_array_equals(props, []);
}, "Specified style");

test(function() {
  const props = nonSerializableProperties(getComputedStyle(target));
  assert_array_equals(props, []);
}, "Computed style");
</script>