gecko-dev/dom/base/test/browser_messagemanager_unload.js

function frameScript()
{
  const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");

  function eventHandler(e) {
    if (!docShell) {
      sendAsyncMessage("Test:Fail", "docShell is null");
    }

    sendAsyncMessage("Test:Event", [e.type, e.target === content.document, e.eventPhase]);
  }

  let outerID = content.windowUtils.outerWindowID;
  function onOuterWindowDestroyed(subject, topic, data) {
    if (docShell) {
      sendAsyncMessage("Test:Fail", "docShell is non-null");
    }

    let id = subject.QueryInterface(Ci.nsISupportsPRUint64).data;
    sendAsyncMessage("Test:Event", ["outer-window-destroyed", id == outerID]);
    if (id == outerID) {
      Services.obs.removeObserver(onOuterWindowDestroyed, "outer-window-destroyed");
    }
  }

  let url = "https://example.com/browser/dom/base/test/file_messagemanager_unload.html";

  content.location = url;
  addEventListener("load", (e) => {
    if (e.target.location != url) {
      return;
    }

    addEventListener("unload", eventHandler, false);
    addEventListener("unload", eventHandler, true);
    addEventListener("pagehide", eventHandler, false);
    addEventListener("pagehide", eventHandler, true);
    Services.obs.addObserver(onOuterWindowDestroyed, "outer-window-destroyed");

    sendAsyncMessage("Test:Ready");
  }, true);
}

const EXPECTED = [
  // Unload events on the TabChildGlobal. These come first so that the
  // docshell is available.
  ["unload", false, 2],
  ["unload", false, 2],

  // pagehide and unload events for the top-level page.
  ["pagehide", true, 1],
  ["pagehide", true, 3],
  ["unload", true, 1],

  // pagehide and unload events for the iframe.
  ["pagehide", false, 1],
  ["pagehide", false, 3],
  ["unload", false, 1],

  // outer-window-destroyed for both pages.
  ["outer-window-destroyed", false],
  ["outer-window-destroyed", true],
];

function test() {
  waitForExplicitFinish();

  var newTab = BrowserTestUtils.addTab(gBrowser, "about:blank");
  gBrowser.selectedTab = newTab;

  let browser = newTab.linkedBrowser;
  let frameLoader = browser.frameLoader;
  ok(frameLoader !== null, "frameLoader looks okay");

  browser.messageManager.loadFrameScript("data:,(" + frameScript.toString() + ")()", false);

  browser.messageManager.addMessageListener("Test:Fail", (msg) => {
    ok(false, msg.data);
  }, true);

  let index = 0;
  browser.messageManager.addMessageListener("Test:Event", (msg) => {
    ok(msg.target === browser, "<browser> is correct");
    ok(msg.targetFrameLoader === frameLoader, "frameLoader is correct");
    ok(browser.frameLoader === null, "browser frameloader null during teardown");

    info(JSON.stringify(msg.data));

    is(JSON.stringify(msg.data), JSON.stringify(EXPECTED[index]), "results match");
    index++;

    if (index == EXPECTED.length) {
      finish();
    }
  }, true);

  browser.messageManager.addMessageListener("Test:Ready", () => {
    info("Got ready message");
    gBrowser.removeCurrentTab();
  });
}