css/cssom-view/GetBoundingRect.html

<!doctype html>
<html>
  <head>
    <meta charset="utf-8">
    <title>getBoundingClientRect</title>
    <link rel="help" href="https://drafts.csswg.org/cssom-view/#dom-element-getboundingclientrect">
    <script src="/resources/testharness.js"></script>
    <script src="/resources/testharnessreport.js"></script>

    <style>
      #foo {
        margin: 0px 0px 0px 5px;
        transform: translate(10px, 200px);
        position: fixed;
        left: 5px;
        background-color: red;
      }
    </style>
  </head>
  <body>
    <div id="foo">
      FOO
    </div>
    <script>
        test(function () {
            var foo = document.getElementById("foo").getBoundingClientRect();
            assert_equals(foo.left, 20);
        });
    </script>
  </body>
</html>