chromium/third_party/blink/web_tests/wpt_internal/css/css-fonts/local-variations.html

<!DOCTYPE html>
<html>
  <head>
    <script src="/resources/testharness.js"></script>
    <script src="/resources/testharnessreport.js"></script>
    <style>
      @font-face {
        font-family: bahnschriftlocal;
        src: local(Bahnschrift);
      }

      .test {
        font-family: bahnschriftlocal;
        font-size: 64px;
      }

      #bahnschrift_narrow {
        font-variation-settings: "wdth" 75;
      }

      #bahnschrift_wide {
        font-variation-settings: "wdht" 100;
      }
    </style>
  </head>

  <div class="test">
    <span id="bahnschrift_narrow">Hamburgefonstiv</span>
    <span id="bahnschrift_wide">Hamburgefonstiv</span>
  </div>
  <script>
    var t = async_test("local() loaded variable font width variation applied.");
    document.fonts.ready.then((fontFaceSet) => {
      var narrow_width = bahnschrift_narrow.getBoundingClientRect().width;
      var wide_width = bahnschrift_wide.getBoundingClientRect().width;
      t.step(function () {
        assert_greater_than(
          wide_width,
          narrow_width + 100,
          "Width variation should be applied."
        );
      });
      t.done();
    });
  </script>
</html>