<!DOCTYPE html>
<meta charset="utf-8">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/helpers.js"></script>

<body>
<script>
"use strict";
promise_test(async t => {
  const sentinelIframe = await setupSentinelIframe(t);
  const startingHistoryLength = history.length;

  const code = `
    const form = document.createElement("form");
    form.action = "/common/blank.html";

    const input = document.createElement("input");
    input.type = "hidden";
    input.name = "thereplacement";
    form.append(input);

    const button = document.createElement("button");
    button.type = "submit";
    form.append(button);

    document.currentScript.before(form);
    button.click();
  `;

  const startURL = "resources/code-injector.html?pipe=sub(none)&code=" + encodeURIComponent(code);
  const afterReplacementURL = "/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, "history.length must not change after waiting for the replacement");

  await checkSentinelIframe(t, sentinelIframe);
  assert_equals(history.length, startingHistoryLength, "history.length must not change after checking the sentinel iframe");
}, "Replace before load, triggered by submitButton.click()");
</script>
