gecko/browser/components/sessionstore/test/browser_833286_atomic_backup.js

/* Any copyright is dedicated to the Public Domain.
   http://creativecommons.org/publicdomain/zero/1.0/ */

// This tests are for a sessionstore.js atomic backup.
// Each test will wait for a write to the Session Store
// before executing.

let tmp = {};
Cu.import("resource://gre/modules/osfile.jsm", tmp);
Cu.import("resource:///modules/sessionstore/SessionFile.jsm", tmp);

const {OS, SessionFile} = tmp;

const PREF_SS_INTERVAL = "browser.sessionstore.interval";
// Full paths for sessionstore.js and sessionstore.bak.
const path = OS.Path.join(OS.Constants.Path.profileDir, "sessionstore.js");
const backupPath = OS.Path.join(OS.Constants.Path.profileDir,
  "sessionstore.bak");

// A text decoder.
let gDecoder = new TextDecoder();
// Global variables that contain sessionstore.js and sessionstore.bak data for
// comparison between tests.
let gSSData;
let gSSBakData;

// Wait for a state write to complete and then execute a callback.
function waitForSaveStateComplete(aSaveStateCallback) {
  let topic = "sessionstore-state-write-complete";

  function observer() {
    Services.prefs.clearUserPref(PREF_SS_INTERVAL);
    Services.obs.removeObserver(observer, topic);
    executeSoon(function taskCallback() {
      Task.spawn(aSaveStateCallback);
    });
  }

  Services.obs.addObserver(observer, topic, false);
}

// Register next test callback and trigger state saving change.
function nextTest(testFunc) {
  waitForSaveStateComplete(testFunc);

  // We set the interval for session store state saves to be zero
  // to cause a save ASAP.
  Services.prefs.setIntPref(PREF_SS_INTERVAL, 0);
}

registerCleanupFunction(function() {
  // Cleaning up after the test: removing the sessionstore.bak file.
  Task.spawn(function cleanupTask() {
    yield OS.File.remove(backupPath);
  });
});

function test() {
  waitForExplicitFinish();
  nextTest(testAfterFirstWrite);
}

function testAfterFirstWrite() {
  // Ensure sessionstore.bak is not created. We start with a clean
  // profile so there was nothing to move to sessionstore.bak before
  // initially writing sessionstore.js
  let ssExists = yield OS.File.exists(path);
  let ssBackupExists = yield OS.File.exists(backupPath);
  ok(ssExists, "sessionstore.js should exist.");
  ok(!ssBackupExists, "sessionstore.bak should not have been created, yet");

  // Save sessionstore.js data to compare to the sessionstore.bak data in the
  // next test.
  let array = yield OS.File.read(path);
  gSSData = gDecoder.decode(array);

  // Manually move to the backup since the first write has already happened
  // and a backup would not be triggered again.
  yield OS.File.move(path, backupPath);

  nextTest(testReadBackup);
}

function testReadBackup() {
  // Ensure sessionstore.bak is finally created.
  let ssExists = yield OS.File.exists(path);
  let ssBackupExists = yield OS.File.exists(backupPath);
  ok(ssExists, "sessionstore.js exists.");
  ok(ssBackupExists, "sessionstore.bak should now be created.");

  // Read sessionstore.bak data.
  let array = yield OS.File.read(backupPath);
  gSSBakData = gDecoder.decode(array);

  // Make sure that the sessionstore.bak is identical to the last
  // sessionstore.js.
  is(gSSBakData, gSSData, "sessionstore.js is backed up correctly.");

  // Read latest sessionstore.js.
  array = yield OS.File.read(path);
  gSSData = gDecoder.decode(array);

  // Read sessionstore.js with SessionFile.read.
  let ssDataRead = yield SessionFile.read();
  is(ssDataRead, gSSData, "SessionFile.read read sessionstore.js correctly.");

  // Remove sessionstore.js to test fallback onto sessionstore.bak.
  yield OS.File.remove(path);
  ssExists = yield OS.File.exists(path);
  ok(!ssExists, "sessionstore.js should be removed now.");

  // Read sessionstore.bak with SessionFile.read.
  ssDataRead = yield SessionFile.read();
  is(ssDataRead, gSSBakData,
    "SessionFile.read read sessionstore.bak correctly.");

  nextTest(testBackupUnchanged);
}

function testBackupUnchanged() {
  // Ensure sessionstore.bak is backed up only once.

  // Read sessionstore.bak data.
  let array = yield OS.File.read(backupPath);
  let ssBakData = gDecoder.decode(array);
  // Ensure the sessionstore.bak did not change.
  is(ssBakData, gSSBakData, "sessionstore.bak is unchanged.");

  executeSoon(finish);
}