<!doctype html>
<script src="/resources/testharness.js"></script>
<script>
  // Wait for after the load event so that the navigation doesn't get converted
  // into a replace navigation.
window.onload = () => step_timeout(() => {
  if (location.search == "?go-back") {
    assert_equals(navigation.entries().length, 2);
    assert_equals(navigation.currentEntry.index, 1);
    // Step 2: Navigate back.
    history.back();
    return;
  }
  if (top.start_key) {
    assert_equals(navigation.entries().length, 2);
    assert_equals(navigation.currentEntry.index, 0);
    // Step 3: Notify parent, which will ensure the same key is used after back navigation.
    top.finish(navigation.currentEntry.key, navigation.currentEntry.id);
    return;
  }
  // Step 1: Record initial key and navigate.
  assert_equals(navigation.entries().length, 1);
  top.start_key = navigation.currentEntry.key;
  top.start_id = navigation.currentEntry.id;
  location.search = "go-back";
}, 0);
</script>
