1 files changed, 158 insertions, 0 deletions
diff --git a/browser/components/sessionstore/test/browser_upgrade_backup.js b/browser/components/sessionstore/test/browser_upgrade_backup.js
new file mode 100644
index 0000000000..fa0e34d421
--- /dev/null
+++ b/browser/components/sessionstore/test/browser_upgrade_backup.js
@@ -0,0 +1,158 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { Preferences } = ChromeUtils.importESModule(
+  "resource://gre/modules/Preferences.sys.mjs"
+);
+
+const Paths = SessionFile.Paths;
+const PREF_UPGRADE = "browser.sessionstore.upgradeBackup.latestBuildID";
+const PREF_MAX_UPGRADE_BACKUPS =
+  "browser.sessionstore.upgradeBackup.maxUpgradeBackups";
+
+/**
+ * Prepares tests by retrieving the current platform's build ID, clearing the
+ * build where the last backup was created and creating arbitrary JSON data
+ * for a new backup.
+ */
+function prepareTest() {
+  let result = {};
+
+  result.buildID = Services.appinfo.platformBuildID;
+  Services.prefs.setCharPref(PREF_UPGRADE, "");
+  result.contents = {
+    "browser_upgrade_backup.js": Math.random(),
+  };
+
+  return result;
+}
+
+/**
+ * Retrieves all upgrade backups and returns them in an array.
+ */
+async function getUpgradeBackups() {
+  let children = await IOUtils.getChildren(Paths.backups);
+
+  return children.filter(path => path.startsWith(Paths.upgradeBackupPrefix));
+}
+
+add_setup(async function () {
+  // Wait until initialization is complete
+  await SessionStore.promiseInitialized;
+});
+
+add_task(async function test_upgrade_backup() {
+  let test = prepareTest();
+  info("Let's check if we create an upgrade backup");
+  await SessionFile.wipe();
+  await IOUtils.writeJSON(Paths.clean, test.contents, {
+    compress: true,
+  });
+  info("Call `SessionFile.read()` to set state to 'clean'");
+  await SessionFile.read();
+  await SessionFile.write(""); // First call to write() triggers the backup
+
+  Assert.equal(
+    Services.prefs.getCharPref(PREF_UPGRADE),
+    test.buildID,
+    "upgrade backup should be set"
+  );
+
+  Assert.ok(
+    await IOUtils.exists(Paths.upgradeBackup),
+    "upgrade backup file has been created"
+  );
+
+  let data = await IOUtils.readJSON(Paths.upgradeBackup, { decompress: true });
+  Assert.deepEqual(
+    test.contents,
+    data,
+    "upgrade backup contains the expected contents"
+  );
+
+  info("Let's check that we don't overwrite this upgrade backup");
+  let newContents = {
+    "something else entirely": Math.random(),
+  };
+  await IOUtils.writeJSON(Paths.clean, newContents, {
+    compress: true,
+  });
+  await SessionFile.write(""); // Next call to write() shouldn't trigger the backup
+  data = await IOUtils.readJSON(Paths.upgradeBackup, { decompress: true });
+  Assert.deepEqual(test.contents, data, "upgrade backup hasn't changed");
+});
+
+add_task(async function test_upgrade_backup_removal() {
+  let test = prepareTest();
+  let maxUpgradeBackups = Preferences.get(PREF_MAX_UPGRADE_BACKUPS, 3);
+  info("Let's see if we remove backups if there are too many");
+  await SessionFile.wipe();
+  await IOUtils.writeJSON(Paths.clean, test.contents, {
+    compress: true,
+  });
+  info("Call `SessionFile.read()` to set state to 'clean'");
+  await SessionFile.read();
+
+  // create dummy backups
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20080101010101", "", {
+    compress: true,
+  });
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20090101010101", "", {
+    compress: true,
+  });
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20100101010101", "", {
+    compress: true,
+  });
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20110101010101", "", {
+    compress: true,
+  });
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20120101010101", "", {
+    compress: true,
+  });
+  await IOUtils.writeUTF8(Paths.upgradeBackupPrefix + "20130101010101", "", {
+    compress: true,
+  });
+
+  // get currently existing backups
+  let backups = await getUpgradeBackups();
+
+  info("Write the session to disk and perform a backup");
+  await SessionFile.write(""); // First call to write() triggers the backup and the cleanup
+
+  // a new backup should have been created (and still exist)
+  is(
+    Services.prefs.getCharPref(PREF_UPGRADE),
+    test.buildID,
+    "upgrade backup should be set"
+  );
+  Assert.ok(
+    await IOUtils.exists(Paths.upgradeBackup),
+    "upgrade backup file has been created"
+  );
+
+  // get currently existing backups and check their count
+  let newBackups = await getUpgradeBackups();
+  is(
+    newBackups.length,
+    maxUpgradeBackups,
+    "expected number of backups are present after removing old backups"
+  );
+
+  // find all backups that were created during the last call to `SessionFile.write("");`
+  // ie, filter out all the backups that have already been present before the call
+  newBackups = newBackups.filter(function (backup) {
+    return !backups.includes(backup);
+  });
+
+  // check that exactly one new backup was created
+  is(newBackups.length, 1, "one new backup was created that was not removed");
+
+  await SessionFile.write(""); // Second call to write() should not trigger anything
+
+  backups = await getUpgradeBackups();
+  is(
+    backups.length,
+    maxUpgradeBackups,
+    "second call to SessionFile.write() didn't create or remove more backups"
+  );
+});