Add UMA to report Preferences File Corruption

chrome/browser/prefs/pref_metrics_service_unittest.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/memory/scoped_ptr.h"
+#include "base/metrics/histogram.h"
+#include "base/metrics/statistics_recorder.h"
+#include "base/prefs/testing_pref_service.h"
+#include "base/values.h"
+#include "chrome/browser/prefs/pref_metrics_service.h"
+#include "chrome/browser/prefs/scoped_user_pref_update.h"
+#include "chrome/test/base/testing_pref_service_syncable.h"
+#include "chrome/test/base/testing_profile.h"
+#include "components/user_prefs/pref_registry_syncable.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+// TestingProfile may register some real preferences; to avoid interference,
+// define fake preferences for testing.
+const char* kTrackedPrefs[] = {
+  "pref_metrics_service_test.pref1",
+  "pref_metrics_service_test.pref2",
+};
+
+const int kTrackedPrefCount = arraysize(kTrackedPrefs);
+
+}  // namespace
+
+class PrefMetricsServiceTest : public testing::Test {
+ protected:
+  virtual void SetUp() {
+    pref1_changed_ = 0;
+    pref2_changed_ = 0;
+    pref1_cleared_ = 0;
+    pref2_cleared_ = 0;
+    pref1_initialized_ = 0;
+    pref2_initialized_ = 0;
+    pref1_unchanged_ = 0;
+    pref2_unchanged_ = 0;
+
+    base::StatisticsRecorder::Initialize();
+
+    prefs_ = profile_.GetTestingPrefService();
+
+    // Register our test-only tracked prefs as string values.
+    for (int i = 0; i < kTrackedPrefCount; ++i) {
+      prefs_->registry()->RegisterStringPref(
+          kTrackedPrefs[i],
+          "test_default_value",
+          user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
+    }
+
+    // Initialize pref in local state that holds hashed values.
+    PrefMetricsService::RegisterPrefs(local_state_.registry());
+
+    // Update global counts in case another test left stray samples.
+    UpdateHistogramSamples();
+  }
+
+  scoped_ptr<PrefMetricsService> CreatePrefMetricsService() {
+    return scoped_ptr<PrefMetricsService>(
+        new PrefMetricsService(&profile_,
+                               &local_state_,
+                               "test_device_id",
+                               kTrackedPrefs,
+                               kTrackedPrefCount));
+  }
+
+  std::string GetHashedPrefValue(PrefMetricsService* service,
+                                 const char* path, base::Value* value) {
+    return service->GetHashedPrefValue(path, value);
+  }
+
+  void GetSamples(const char* histogram_name, int* bucket1, int* bucket2) {
+    base::HistogramBase* histogram =
+        base::StatisticsRecorder::FindHistogram(histogram_name);
+    if (!histogram) {
+      *bucket1 = 0;
+      *bucket2 = 0;
+    } else {
+      scoped_ptr<base::HistogramSamples> samples(histogram->SnapshotSamples());
+      *bucket1 = samples->GetCount(0);
+      *bucket2 = samples->GetCount(1);
+    }
+  }
+
+  void UpdateHistogramSamples() {
+    int changed1, changed2;
+    GetSamples("Settings.TrackedPreferenceChanged", &changed1, &changed2);
+    pref1_changed_ = changed1 - pref1_changed_total;
+    pref2_changed_ = changed2 - pref2_changed_total;
+    pref1_changed_total = changed1;
+    pref2_changed_total = changed2;
+
+    int cleared1, cleared2;
+    GetSamples("Settings.TrackedPreferenceCleared", &cleared1, &cleared2);
+    pref1_cleared_ = cleared1 - pref1_cleared_total;
+    pref2_cleared_ = cleared2 - pref2_cleared_total;
+    pref1_cleared_total = cleared1;
+    pref2_cleared_total = cleared2;
+
+    int inited1, inited2;
+    GetSamples("Settings.TrackedPreferenceInitialized", &inited1, &inited2);
+    pref1_initialized_ = inited1 - pref1_initialized_total;
+    pref2_initialized_ = inited2 - pref2_initialized_total;
+    pref1_initialized_total = inited1;
+    pref2_initialized_total = inited2;
+
+    int unchanged1, unchanged2;
+    GetSamples("Settings.TrackedPreferenceUnchanged", &unchanged1, &unchanged2);
+    pref1_unchanged_ = unchanged1 - pref1_unchanged_total;
+    pref2_unchanged_ = unchanged2 - pref2_unchanged_total;
+    pref1_unchanged_total = unchanged1;
+    pref2_unchanged_total = unchanged2;
+  }
+
+  TestingProfile profile_;
+  TestingPrefServiceSyncable* prefs_;
+  TestingPrefServiceSimple local_state_;
+
+  // Since histogram samples are recorded by a global StatisticsRecorder, we
+  // need to maintain total counts so we can compute deltas for individual
+  // tests.
+  static int pref1_changed_total;
+  static int pref2_changed_total;
+  static int pref1_cleared_total;
+  static int pref2_cleared_total;
+  static int pref1_initialized_total;
+  static int pref2_initialized_total;
+  static int pref1_unchanged_total;
+  static int pref2_unchanged_total;
+
+  // Counts of samples recorded since UpdateHistogramSamples was last called.
+  int pref1_changed_;
+  int pref2_changed_;
+  int pref1_cleared_;
+  int pref2_cleared_;
+  int pref1_initialized_;
+  int pref2_initialized_;
+  int pref1_unchanged_;
+  int pref2_unchanged_;
+};
+
+int PrefMetricsServiceTest::pref1_changed_total;
+int PrefMetricsServiceTest::pref2_changed_total;
+int PrefMetricsServiceTest::pref1_cleared_total;
+int PrefMetricsServiceTest::pref2_cleared_total;
+int PrefMetricsServiceTest::pref1_initialized_total;
+int PrefMetricsServiceTest::pref2_initialized_total;
+int PrefMetricsServiceTest::pref1_unchanged_total;
+int PrefMetricsServiceTest::pref2_unchanged_total;
+
+TEST_F(PrefMetricsServiceTest, StartupNoUserPref) {
+  // Local state is empty and no user prefs are set. We should record that we
+  // checked preferences once but since there are no user preference values, no
+  // other histogram data should be collected.
+  scoped_ptr<PrefMetricsService> test = CreatePrefMetricsService();
+  UpdateHistogramSamples();
+  EXPECT_EQ(0, pref1_changed_);
+  EXPECT_EQ(0, pref2_changed_);
+  EXPECT_EQ(0, pref1_cleared_);
+  EXPECT_EQ(0, pref2_cleared_);
+  EXPECT_EQ(0, pref1_initialized_);
+  EXPECT_EQ(0, pref2_initialized_);
+  EXPECT_EQ(1, pref1_unchanged_);
+  EXPECT_EQ(1, pref2_unchanged_);
+}
+
+TEST_F(PrefMetricsServiceTest, StartupUserPref) {
+  // Local state is empty. Set a value for one tracked pref. We should record
+  // that we checked preferences once and initialized a hash for the pref.
+  prefs_->SetString(kTrackedPrefs[0], "foo");
+  {
+    scoped_ptr<PrefMetricsService> test = CreatePrefMetricsService();
+    UpdateHistogramSamples();
+    EXPECT_EQ(0, pref1_changed_);
+    EXPECT_EQ(0, pref2_changed_);
+    EXPECT_EQ(0, pref1_cleared_);
+    EXPECT_EQ(0, pref2_cleared_);
+    EXPECT_EQ(1, pref1_initialized_);
+    EXPECT_EQ(0, pref2_initialized_);
+    EXPECT_EQ(0, pref1_unchanged_);
+    EXPECT_EQ(1, pref2_unchanged_);
+
+    // Change the pref. This should be observed by the PrefMetricsService, which
+    // will update the hash in local_state_ to stay in sync.
+    prefs_->SetString(kTrackedPrefs[0], "bar");
+  }
+  // The next startup should record no changes.
+  {
+    scoped_ptr<PrefMetricsService> test = CreatePrefMetricsService();
+    UpdateHistogramSamples();
+    EXPECT_EQ(0, pref1_changed_);
+    EXPECT_EQ(0, pref2_changed_);
+    EXPECT_EQ(0, pref1_cleared_);
+    EXPECT_EQ(0, pref2_cleared_);
+    EXPECT_EQ(0, pref1_initialized_);
+    EXPECT_EQ(0, pref2_initialized_);
+    EXPECT_EQ(1, pref1_unchanged_);
+    EXPECT_EQ(1, pref2_unchanged_);
+  }
+}
+
+TEST_F(PrefMetricsServiceTest, ChangedUserPref) {
+  // Local state is empty. Set a value for the tracked pref. We should record
+  // that we checked preferences once and initialized a hash for the pref.
+  prefs_->SetString(kTrackedPrefs[0], "foo");
+  {
+    scoped_ptr<PrefMetricsService> test = CreatePrefMetricsService();
+    UpdateHistogramSamples();
+    EXPECT_EQ(0, pref1_changed_);
+    EXPECT_EQ(0, pref2_changed_);
+    EXPECT_EQ(0, pref1_cleared_);
+    EXPECT_EQ(0, pref2_cleared_);
+    EXPECT_EQ(1, pref1_initialized_);
+    EXPECT_EQ(0, pref2_initialized_);
+    EXPECT_EQ(0, pref1_unchanged_);
+    EXPECT_EQ(1, pref2_unchanged_);
+    // Hashed prefs should now be stored in local state.
+  }
+  // Change the value of the tracked pref while there is no PrefMetricsService
+  // to update the hash. We should observe a pref value change.
+  prefs_->SetString(kTrackedPrefs[0], "bar");
+  {
+    scoped_ptr<PrefMetricsService> test = CreatePrefMetricsService();
+    UpdateHistogramSamples();
+    EXPECT_EQ(1, pref1_changed_);
+    EXPECT_EQ(0, pref2_changed_);
+    EXPECT_EQ(0, pref1_cleared_);
+    EXPECT_EQ(0, pref2_cleared_);
+    EXPECT_EQ(0, pref1_initialized_);
+    EXPECT_EQ(0, pref2_initialized_);
+    EXPECT_EQ(0, pref1_unchanged_);
+    EXPECT_EQ(1, pref2_unchanged_);
+  }
+  // Clear the value of the tracked pref while there is no PrefMetricsService
+  // to update the hash. We should observe a pref value removal.
+  prefs_->ClearPref(kTrackedPrefs[0]);
+  {
+    scoped_ptr<PrefMetricsService> test = CreatePrefMetricsService();
+    UpdateHistogramSamples();
+    EXPECT_EQ(0, pref1_changed_);
+    EXPECT_EQ(0, pref2_changed_);
+    EXPECT_EQ(1, pref1_cleared_);
+    EXPECT_EQ(0, pref2_cleared_);
+    EXPECT_EQ(0, pref1_initialized_);
+    EXPECT_EQ(0, pref2_initialized_);
+    EXPECT_EQ(0, pref1_unchanged_);
+    EXPECT_EQ(1, pref2_unchanged_);
+  }
+}
+
+// Tests that serialization of dictionary values is stable. If the order of
+// the entries or any whitespace changes, it would cause a spike in pref change
+// UMA events as every hash would change.
+TEST_F(PrefMetricsServiceTest, PrefHashStability) {
+  scoped_ptr<PrefMetricsService> test = CreatePrefMetricsService();
+  DictionaryValue dict;
+  dict.Set("a", new StringValue("foo"));
+  dict.Set("b", new StringValue("bar"));
+  dict.Set("c", new StringValue("baz"));
+  dict.Set("d", new StringValue("bad"));

[battre, 2013/09/06 11:35:33]

Please move this line 3 lines up to confirm that the insertion order does not
matter.

Ii would also add a list and some other values that may break the hash values if
their serialization changes.

[bbudge, 2013/09/06 13:31:34]

Done.

+  std::string hash = GetHashedPrefValue(test.get(), "pref.path", &dict);
+  EXPECT_EQ("C503FB7C65EEFD5C07185F616A0AA67923C069909933F362022B1F187E73E9A2",
+            hash);
+}