[PATCH 2/2] Bug 833286 - added tests for improvements to atomic backup of sessionstore.js. r=yoric, ttaubert

---
 browser/components/sessionstore/test/Makefile.in   |    1 +
 .../test/browser_833286_atomic_backup.js           |  143 ++++++++++++++++++++
 2 files changed, 144 insertions(+), 0 deletions(-)
 create mode 100644 browser/components/sessionstore/test/browser_833286_atomic_backup.js

browser/components/sessionstore/test/Makefile.in

@@ -139,6 +139,7 @@ MOCHITEST_BROWSER_FILES = \
 	browser_739531_sample.html \
 	browser_739805.js \
 	browser_819510_perwindowpb.js \
+	browser_833286_atomic_backup.js \
 	$(filter disabled-for-intermittent-failures--bug-766044, browser_459906_empty.html) \
 	$(filter disabled-for-intermittent-failures--bug-766044, browser_459906_sample.html) \
 	$(filter disabled-for-intermittent-failures--bug-765389, browser_461743_sample.html) \

browser/components/sessionstore/test/browser_833286_atomic_backup.js

@@ -0,0 +1,143 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// This tests are for a sessionstore.js atomic backup.
+
+let tmp = {};
+Cu.import("resource://gre/modules/osfile.jsm", tmp);
+Cu.import("resource://gre/modules/Task.jsm", tmp);
+Cu.import("resource:///modules/sessionstore/_SessionFile.jsm", tmp);
+
+const {OS, Task, _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;
+
+// waitForSaveStateComplete waits for a state write completion.
+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);
+  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(testInitialWriteNoBackup);
+}
+
+function testInitialWriteNoBackup() {
+  // Ensure that sessionstore.js is created, but not sessionstore.bak.
+  let ssExists = yield OS.File.exists(path);
+  let ssBackupExists = yield OS.File.exists(backupPath);
+  ok(ssExists, "sessionstore.js should be created.");
+  ok(!ssBackupExists, "sessionstore.bak should not have been created, yet.");
+
+  nextTest(testWriteNoBackup);
+}
+
+function testWriteNoBackup() {
+  // Ensure sessionstore.bak is not created.
+  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 trigger _SessionFile.createBackupCopy since the backup once
+  // promise is already resolved and backup would not be triggered again.
+  yield _SessionFile.createBackupCopy();
+
+  nextTest(testWriteBackup);
+}
+
+function testWriteBackup() {
+  // 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.");
+
+  // Read sessionstore.js with _SessionFile.syncRead.
+  ssDataRead = _SessionFile.syncRead();
+  is(ssDataRead, gSSData,
+    "_SessionFile.syncRead 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.");
+
+  // Read sessionstore.bak with _SessionFile.syncRead.
+  ssDataRead = _SessionFile.syncRead();
+  is(ssDataRead, gSSBakData,
+    "_SessionFile.syncRead read sessionstore.bak correctly.");
+  nextTest(testNoWriteBackup);
+}
+
+function testNoWriteBackup() {
+  // 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);
+}