navigation-api/scroll-behavior/manual-scroll-before-after-transition-commit.html

<!doctype html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<body>
<div style="height: 1000px; width: 1000px;"></div>
<div id="frag"></div>
<script>
promise_test(async t => {
  // Wait for after the load event so that the navigation doesn't get converted
  // into a replace navigation.
  await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
  assert_equals(window.scrollY, 0);
  await navigation.navigate("#frag").finished;
  assert_not_equals(window.scrollY, 0);
  navigation.onnavigate = e => {
    e.intercept({
      scroll: "manual",
      commit: "after-transition",
      handler: t.step_func(() => {
        assert_throws_dom("InvalidStateError", () => e.scroll());
        assert_not_equals(window.scrollY, 0);
        e.commit();
        e.scroll();
        assert_equals(window.scrollY, 0);
      })
    });
  }
  await navigation.back().finished;
  assert_equals(window.scrollY, 0);
}, "scroll: scroll() before commit()");
</script>
</body>