navigation-api/navigate-event/navigate-history-back-noop.html

<!doctype html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<iframe id="i" src="/common/blank.html"></iframe>
<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));

  await i.contentWindow.navigation.navigate("#").finished;
  assert_equals(i.contentWindow.navigation.entries().length, 2);
  assert_equals(i.contentWindow.navigation.currentEntry.index, 1);
  assert_equals(navigation.entries().length, 1);
  assert_equals(navigation.currentEntry.index, 0);
  assert_equals(history.length, 2);

  i.remove();
  assert_equals(navigation.entries().length, 1);
  assert_equals(navigation.currentEntry.index, 0);
  assert_equals(history.length, 2);

  // back() here should do nothing. The iframe that would have navigated has
  // been removed. No navigate event should be fired.
  navigation.onnavigate = t.unreached_func("navigate must not fire");
  navigation.oncurrententrychange = t.unreached_func("currententrychange must not fire");
  history.back();

  // Give time for the navigation to proceed.
  await new Promise(resolve => t.step_timeout(resolve, 20));
}, "history.back() does not fire a navigate event when there's nothing to navigate");
</script>