lacementURL = "/common/blank.html?thereplacement";
  const iframe = insertIframe(t, startURL);

  assert_equals(history.length, startingHistoryLength, "Inserting the under-test iframe must not change history.length");

  await waitForLoad(t, iframe, afterReplacementURL);
  assert_equals(history.length, startingHistoryLength + 1, "history.length must change after waiting for the load");
}, "href");

promise_test(async t => {
  const sentinelIframe = await setupSentinelIframe(t);
  const startingHistoryLength