sync: beginnings of MessageLoop based SyncerThread

chrome/browser/sync/engine/syncer_thread2_unittest.cc

+// Copyright (c) 2011 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/synchronization/waitable_event.h"
+#include "base/test/test_timeouts.h"
+#include "chrome/browser/sync/engine/mock_model_safe_workers.h"
+#include "chrome/browser/sync/engine/syncer.h"
+#include "chrome/browser/sync/engine/syncer_thread2.h"
+#include "chrome/browser/sync/sessions/test_util.h"
+#include "chrome/test/sync/engine/test_directory_setter_upper.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/gmock/include/gmock/gmock.h"
+
+using base::TimeDelta;
+using base::TimeTicks;
+using testing::_;
+using testing::AtLeast;
+using testing::DoAll;
+using testing::Eq;
+using testing::Invoke;
+using testing::Mock;
+using testing::Return;
+using testing::WithArg;
+
+namespace browser_sync {
+using sessions::SyncSession;
+using sessions::SyncSessionContext;
+using sessions::SyncSessionSnapshot;
+using syncable::ModelTypeBitSet;
+using sync_pb::GetUpdatesCallerInfo;
+
+class MockSyncer : public Syncer {
+ public:
+  MOCK_METHOD1(SyncShare, void(sessions::SyncSession*));
+};
+
+namespace s3 {
+
+// Used when tests want to record syncing activity to examine later.
+struct SyncShareRecords {
+  std::vector<TimeTicks> times;
+  std::vector<linked_ptr<SyncSessionSnapshot> > snapshots;
+};
+
+// Convenient to use in tests wishing to analyze SyncShare calls over time.
+static const size_t kMinNumSamples = 5;
+
+class SyncerThread2Test : public testing::Test {
+ public:
+  class MockDelayProvider : public SyncerThread::DelayProvider {
+   public:
+    MOCK_METHOD1(GetDelay, TimeDelta(const TimeDelta&));
+  };
+
+  virtual void SetUp() {
+    syncdb_.SetUp();
+    syncer_ = new MockSyncer();
+    delay_ = NULL;
+    registrar_.reset(MockModelSafeWorkerRegistrar::PassiveBookmarks());
+    context_ = new SyncSessionContext(NULL, syncdb_.manager(),
+        registrar_.get(), std::vector<SyncEngineEventListener*>());
+    context_->set_notifications_enabled(true);
+    context_->set_account_name("Test");
+    syncer_thread_.reset(new SyncerThread(context_, syncer_));
+    // TODO(tim): Once the SCM is hooked up, remove this.
+    syncer_thread_->server_connection_ok_ = true;
+  }
+
+  SyncerThread* syncer_thread() { return syncer_thread_.get(); }
+  MockSyncer* syncer() { return syncer_; }
+  MockDelayProvider* delay() { return delay_; }
+  TimeDelta zero() { return TimeDelta::FromSeconds(0); }
+  TimeDelta timeout() {
+    return TimeDelta::FromMilliseconds(TestTimeouts::action_timeout_ms());
+  }
+
+  virtual void TearDown() {
+    syncer_thread()->Stop();
+    syncdb_.TearDown();
+  }
+
+  void AnalyzePollRun(const SyncShareRecords& records, size_t min_num_samples,
+      const TimeTicks& optimal_start, const TimeDelta& poll_interval) {
+    const std::vector<TimeTicks>& data(records.times);
+    EXPECT_GE(data.size(), min_num_samples);
+    for (size_t i = 0; i < data.size(); i++) {
+      SCOPED_TRACE(testing::Message() << "SyncShare # (" << i << ")");
+      TimeTicks optimal_next_sync = optimal_start + poll_interval * i;
+      EXPECT_GE(data[i], optimal_next_sync);
+      EXPECT_LT(data[i], optimal_next_sync + poll_interval);
+      EXPECT_EQ(GetUpdatesCallerInfo::PERIODIC,
+                records.snapshots[i]->source.first);
+    }
+  }
+
+  bool GetBackoffAndResetTest(base::WaitableEvent* done) {
+    syncable::ModelTypeBitSet nudge_types;
+    syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+    syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_LOCAL, nudge_types);
+    done->TimedWait(timeout());
+    TearDown();
+    done->Reset();
+    Mock::VerifyAndClearExpectations(syncer());
+    bool backing_off = syncer_thread()->IsBackingOff();
+    SetUp();
+    UseMockDelayProvider();
+    EXPECT_CALL(*delay(), GetDelay(_))
+        .WillRepeatedly(Return(TimeDelta::FromMilliseconds(1)));
+    return backing_off;
+  }
+
+  void UseMockDelayProvider() {
+    delay_ = new MockDelayProvider();
+    syncer_thread_->delay_provider_.reset(delay_);
+  }
+
+  void PostSignalTask(base::WaitableEvent* done) {
+    syncer_thread_->thread_.message_loop()->PostTask(FROM_HERE,
+        NewRunnableFunction(&SyncerThread2Test::SignalWaitableEvent, done));
+  }
+
+  void FlushLastTask(base::WaitableEvent* done) {
+    PostSignalTask(done);
+    done->TimedWait(timeout());
+    done->Reset();
+  }
+
+  static void SignalWaitableEvent(base::WaitableEvent* event) {
+    event->Signal();
+  }
+
+ private:
+  scoped_ptr<SyncerThread> syncer_thread_;
+  SyncSessionContext* context_;
+  MockSyncer* syncer_;
+  MockDelayProvider* delay_;
+  scoped_ptr<MockModelSafeWorkerRegistrar> registrar_;
+  MockDirectorySetterUpper syncdb_;
+};
+
+bool RecordSyncShareImpl(SyncSession* s, SyncShareRecords* record,
+                         size_t signal_after) {
+  record->times.push_back(TimeTicks::Now());
+  record->snapshots.push_back(make_linked_ptr(new SyncSessionSnapshot(
+      s->TakeSnapshot())));
+  return record->times.size() >= signal_after;
+}
+
+ACTION_P4(RecordSyncShareAndPostSignal, record, signal_after, test, event) {
+  if (RecordSyncShareImpl(arg0, record, signal_after) && event)
+    test->PostSignalTask(event);
+}
+
+ACTION_P3(RecordSyncShare, record, signal_after, event) {
+  if (RecordSyncShareImpl(arg0, record, signal_after) && event)
+    event->Signal();
+}
+
+ACTION_P(SignalEvent, event) {
+  SyncerThread2Test::SignalWaitableEvent(event);
+}
+
+// Test nudge scheduling.
+TEST_F(SyncerThread2Test, Nudge) {
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  base::WaitableEvent done(false, false);
+  SyncShareRecords records;
+  syncable::ModelTypeBitSet model_types;
+  model_types[syncable::BOOKMARKS] = true;
+
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+          WithArg<0>(RecordSyncShare(&records, 1U, &done))));
+  syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_LOCAL, model_types);
+  done.TimedWait(timeout());
+
+  EXPECT_EQ(1U, records.snapshots.size());
+  EXPECT_EQ(model_types, records.snapshots[0]->source.second);
+  EXPECT_EQ(GetUpdatesCallerInfo::LOCAL, records.snapshots[0]->source.first);
+}
+
+// Test that nudges are coalesced.
+TEST_F(SyncerThread2Test, NudgeCoalescing) {
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  base::WaitableEvent done(false, false);
+  SyncShareRecords r;
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+           WithArg<0>(RecordSyncShare(&r, 1U, &done))));
+  syncable::ModelTypeBitSet types1, types2, types3;
+  types1[syncable::BOOKMARKS] = true;
+  types2[syncable::AUTOFILL] = true;
+  types3[syncable::THEMES] = true;
+  TimeDelta delay = TimeDelta::FromMilliseconds(20);
+  TimeTicks optimal_time = TimeTicks::Now() + delay;
+  syncer_thread()->ScheduleNudge(delay, NUDGE_SOURCE_UNKNOWN, types1);
+  syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_LOCAL, types2);
+  syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_NOTIFICATION, types3);
+  done.TimedWait(timeout());
+
+  EXPECT_EQ(1U, r.snapshots.size());
+  EXPECT_GE(r.times[0], optimal_time);
+  EXPECT_EQ(types1 | types2 | types3, r.snapshots[0]->source.second);
+  EXPECT_EQ(GetUpdatesCallerInfo::NOTIFICATION, r.snapshots[0]->source.first);
+
+  SyncShareRecords r2;
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+           WithArg<0>(RecordSyncShare(&r2, 1U, &done))));
+  syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_NOTIFICATION, types3);
+  done.TimedWait(timeout());
+  EXPECT_EQ(1U, r2.snapshots.size());
+  EXPECT_EQ(types3, r2.snapshots[0]->source.second);
+  EXPECT_EQ(GetUpdatesCallerInfo::NOTIFICATION, r2.snapshots[0]->source.first);
+}
+
+// Test that polling works as expected.
+TEST_F(SyncerThread2Test, Polling) {
+  SyncShareRecords records;
+  base::WaitableEvent done(false, false);
+  TimeDelta poll_interval(TimeDelta::FromMilliseconds(30));
+  syncer_thread()->OnReceivedLongPollIntervalUpdate(poll_interval);
+  EXPECT_CALL(*syncer(), SyncShare(_)).Times(AtLeast(kMinNumSamples))
+      .WillRepeatedly(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+           WithArg<0>(RecordSyncShare(&records, kMinNumSamples, &done))));
+
+  TimeTicks optimal_start = TimeTicks::Now() + poll_interval;
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  done.TimedWait(timeout());
+  syncer_thread()->Stop();
+
+  AnalyzePollRun(records, kMinNumSamples, optimal_start, poll_interval);
+}
+
+// Test that the short poll interval is used.
+TEST_F(SyncerThread2Test, PollNotificationsDisabled) {
+  SyncShareRecords records;
+  base::WaitableEvent done(false, false);
+  TimeDelta poll_interval(TimeDelta::FromMilliseconds(30));
+  syncer_thread()->OnReceivedShortPollIntervalUpdate(poll_interval);
+  syncer_thread()->set_notifications_enabled(false);
+  EXPECT_CALL(*syncer(), SyncShare(_)).Times(AtLeast(kMinNumSamples))
+      .WillRepeatedly(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+           WithArg<0>(RecordSyncShare(&records, kMinNumSamples, &done))));
+
+  TimeTicks optimal_start = TimeTicks::Now() + poll_interval;
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  done.TimedWait(timeout());
+  syncer_thread()->Stop();
+
+  AnalyzePollRun(records, kMinNumSamples, optimal_start, poll_interval);
+}
+
+// Test that polling intervals are updated when needed.
+TEST_F(SyncerThread2Test, PollIntervalUpdate) {
+  SyncShareRecords records;
+  base::WaitableEvent done(false, false);
+  TimeDelta poll1(TimeDelta::FromMilliseconds(120));
+  TimeDelta poll2(TimeDelta::FromMilliseconds(30));
+  syncer_thread()->OnReceivedLongPollIntervalUpdate(poll1);
+  EXPECT_CALL(*syncer(), SyncShare(_)).Times(AtLeast(kMinNumSamples))
+      .WillOnce(WithArg<0>(
+          sessions::test_util::SimulatePollIntervalUpdate(poll2)))
+      .WillRepeatedly(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+           WithArg<0>(RecordSyncShare(&records, kMinNumSamples, &done))));
+
+  TimeTicks optimal_start = TimeTicks::Now() + poll1 + poll2;
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  done.TimedWait(timeout());
+  syncer_thread()->Stop();
+
+  AnalyzePollRun(records, kMinNumSamples, optimal_start, poll2);
+}
+
+// Test that a sync session is run through to completion.
+TEST_F(SyncerThread2Test, HasMoreToSync) {
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  base::WaitableEvent done(false, false);
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(Invoke(sessions::test_util::SimulateHasMoreToSync))
+      .WillOnce(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+                      SignalEvent(&done)));
+  syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_LOCAL, ModelTypeBitSet());
+  done.TimedWait(timeout());
+  // If more nudges are scheduled, they'll be waited on by TearDown, and would
+  // cause our expectation to break.
+}
+
+// Test that no syncing occurs when throttled.
+TEST_F(SyncerThread2Test, ThrottlingDoesThrottle) {
+  syncable::ModelTypeBitSet types;
+  types[syncable::BOOKMARKS] = true;
+  base::WaitableEvent done(false, false);
+  TimeDelta poll(TimeDelta::FromMilliseconds(5));
+  TimeDelta throttle(TimeDelta::FromMinutes(10));
+  syncer_thread()->OnReceivedLongPollIntervalUpdate(poll);
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(WithArg<0>(sessions::test_util::SimulateThrottled(throttle)));
+
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_LOCAL, types);
+  FlushLastTask(&done);
+
+  syncer_thread()->Start(SyncerThread::CONFIGURATION_MODE);
+  syncer_thread()->ScheduleConfig(zero(), types);
+  FlushLastTask(&done);
+}
+
+TEST_F(SyncerThread2Test, ThrottlingExpires) {
+  SyncShareRecords records;
+  base::WaitableEvent done(false, false);
+  TimeDelta poll(TimeDelta::FromMilliseconds(15));
+  TimeDelta throttle1(TimeDelta::FromMilliseconds(150));
+  TimeDelta throttle2(TimeDelta::FromMinutes(10));
+  syncer_thread()->OnReceivedLongPollIntervalUpdate(poll);
+
+  ::testing::InSequence seq;
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(WithArg<0>(sessions::test_util::SimulateThrottled(throttle1)))
+      .RetiresOnSaturation();
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillRepeatedly(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+           WithArg<0>(RecordSyncShare(&records, kMinNumSamples, &done))));
+
+  TimeTicks optimal_start = TimeTicks::Now() + poll + throttle1;
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  done.TimedWait(timeout());
+  syncer_thread()->Stop();
+
+  AnalyzePollRun(records, kMinNumSamples, optimal_start, poll);
+}
+
+// Test nudges / polls don't run in config mode and config tasks do.
+TEST_F(SyncerThread2Test, ConfigurationMode) {
+  TimeDelta poll(TimeDelta::FromMilliseconds(15));
+  base::WaitableEvent done(false, false);
+  syncer_thread()->OnReceivedLongPollIntervalUpdate(poll);
+  EXPECT_CALL(*syncer(), SyncShare(_)).Times(0);
+  syncer_thread()->Start(SyncerThread::CONFIGURATION_MODE);
+  syncable::ModelTypeBitSet nudge_types;
+  nudge_types[syncable::AUTOFILL] = true;
+  syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_LOCAL, nudge_types);
+  syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_LOCAL, nudge_types);
+
+  syncable::ModelTypeBitSet config_types;
+  config_types[syncable::BOOKMARKS] = true;
+  // TODO(tim): This will fail once CONFIGURATION tasks are implemented. Update
+  // the EXPECT when that happens.
+  syncer_thread()->ScheduleConfig(zero(), config_types);
+  FlushLastTask(&done);
+}
+
+// Test that exponential backoff is properly triggered.
+TEST_F(SyncerThread2Test, BackoffTriggers) {
+  base::WaitableEvent done(false, false);
+  UseMockDelayProvider();
+
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(Invoke(sessions::test_util::SimulateDownloadUpdatesFailed))
+      .WillOnce(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+          SignalEvent(&done)));
+  EXPECT_FALSE(GetBackoffAndResetTest(&done));
+  // Note GetBackoffAndResetTest clears mocks and re-instantiates the syncer.
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(Invoke(sessions::test_util::SimulateCommitFailed))
+      .WillOnce(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+          SignalEvent(&done)));
+  EXPECT_FALSE(GetBackoffAndResetTest(&done));
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(Invoke(sessions::test_util::SimulateDownloadUpdatesFailed))
+      .WillRepeatedly(DoAll(Invoke(
+          sessions::test_util::SimulateDownloadUpdatesFailed),
+          SignalEvent(&done)));
+  EXPECT_TRUE(GetBackoffAndResetTest(&done));
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(Invoke(sessions::test_util::SimulateCommitFailed))
+      .WillRepeatedly(DoAll(Invoke(sessions::test_util::SimulateCommitFailed),
+          SignalEvent(&done)));
+  EXPECT_TRUE(GetBackoffAndResetTest(&done));
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(Invoke(sessions::test_util::SimulateDownloadUpdatesFailed))
+      .WillOnce(Invoke(sessions::test_util::SimulateDownloadUpdatesFailed))
+      .WillRepeatedly(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+          SignalEvent(&done)));
+  EXPECT_FALSE(GetBackoffAndResetTest(&done));
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(Invoke(sessions::test_util::SimulateCommitFailed))
+      .WillOnce(Invoke(sessions::test_util::SimulateCommitFailed))
+      .WillRepeatedly(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+          SignalEvent(&done)));
+  EXPECT_FALSE(GetBackoffAndResetTest(&done));
+}
+
+// Test that no polls or extraneous nudges occur when in backoff.
+TEST_F(SyncerThread2Test, BackoffDropsJobs) {
+  SyncShareRecords r;
+  TimeDelta poll(TimeDelta::FromMilliseconds(5));
+  base::WaitableEvent done(false, false);
+  syncable::ModelTypeBitSet types;
+  types[syncable::BOOKMARKS] = true;
+  syncer_thread()->OnReceivedLongPollIntervalUpdate(poll);
+  UseMockDelayProvider();
+
+  EXPECT_CALL(*syncer(), SyncShare(_)).Times(2)
+      .WillRepeatedly(DoAll(Invoke(sessions::test_util::SimulateCommitFailed),
+          RecordSyncShareAndPostSignal(&r, 2U, this, &done)));
+  EXPECT_CALL(*delay(), GetDelay(_))
+      .WillRepeatedly(Return(TimeDelta::FromDays(1)));
+
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  ASSERT_TRUE(done.TimedWait(timeout()));
+  done.Reset();
+
+  Mock::VerifyAndClearExpectations(syncer());
+  EXPECT_EQ(2U, r.snapshots.size());
+  EXPECT_EQ(GetUpdatesCallerInfo::PERIODIC, r.snapshots[0]->source.first);
+  EXPECT_EQ(GetUpdatesCallerInfo::SYNC_CYCLE_CONTINUATION,
+            r.snapshots[1]->source.first);
+
+  EXPECT_CALL(*syncer(), SyncShare(_)).Times(1)
+      .WillOnce(DoAll(Invoke(sessions::test_util::SimulateCommitFailed),
+          RecordSyncShareAndPostSignal(&r, 1U, this, &done)));
+
+  // We schedule a nudge with enough delay (10X poll interval) that at least
+  // one or two polls would have taken place.  The nudge should succeed.
+  syncer_thread()->ScheduleNudge(poll * 10, NUDGE_SOURCE_LOCAL, types);
+  ASSERT_TRUE(done.TimedWait(timeout()));
+  done.Reset();
+
+  Mock::VerifyAndClearExpectations(syncer());
+  Mock::VerifyAndClearExpectations(delay());
+  EXPECT_EQ(3U, r.snapshots.size());
+  EXPECT_EQ(GetUpdatesCallerInfo::LOCAL, r.snapshots[2]->source.first);
+
+  EXPECT_CALL(*syncer(), SyncShare(_)).Times(0);
+  EXPECT_CALL(*delay(), GetDelay(_)).Times(0);
+
+  syncer_thread()->Start(SyncerThread::CONFIGURATION_MODE);
+  syncer_thread()->ScheduleConfig(zero(), types);
+  FlushLastTask(&done);
+
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_LOCAL, types);
+  syncer_thread()->ScheduleNudge(zero(), NUDGE_SOURCE_LOCAL, types);
+  FlushLastTask(&done);
+}
+
+// Test that backoff is shaping traffic properly with consecutive errors.
+TEST_F(SyncerThread2Test, BackoffElevation) {
+  SyncShareRecords r;
+  const TimeDelta poll(TimeDelta::FromMilliseconds(10));
+  base::WaitableEvent done(false, false);
+  syncer_thread()->OnReceivedLongPollIntervalUpdate(poll);
+  UseMockDelayProvider();
+
+  const TimeDelta first = TimeDelta::FromSeconds(1);
+  const TimeDelta second = TimeDelta::FromMilliseconds(10);
+  const TimeDelta third = TimeDelta::FromMilliseconds(20);
+  const TimeDelta fourth = TimeDelta::FromMilliseconds(30);
+  const TimeDelta fifth = TimeDelta::FromDays(1);
+
+  EXPECT_CALL(*syncer(), SyncShare(_)).Times(kMinNumSamples)
+      .WillRepeatedly(DoAll(Invoke(sessions::test_util::SimulateCommitFailed),
+          RecordSyncShareAndPostSignal(&r, kMinNumSamples, this, &done)));
+
+  EXPECT_CALL(*delay(), GetDelay(Eq(first))).WillOnce(Return(second))
+      .RetiresOnSaturation();
+  EXPECT_CALL(*delay(), GetDelay(Eq(second))).WillOnce(Return(third))
+      .RetiresOnSaturation();
+  EXPECT_CALL(*delay(), GetDelay(Eq(third))).WillOnce(Return(fourth))
+      .RetiresOnSaturation();
+  EXPECT_CALL(*delay(), GetDelay(Eq(fourth))).WillOnce(Return(fifth));
+
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  ASSERT_TRUE(done.TimedWait(timeout()));
+
+  EXPECT_GE(r.times[2] - r.times[1], second);
+  EXPECT_GE(r.times[3] - r.times[2], third);
+  EXPECT_GE(r.times[4] - r.times[3], fourth);
+}
+
+// Test that things go back to normal once a canary task makes forward progress
+// following a succession of failures.
+TEST_F(SyncerThread2Test, BackoffRelief) {
+  SyncShareRecords r;
+  const TimeDelta poll(TimeDelta::FromMilliseconds(10));
+  base::WaitableEvent done(false, false);
+  syncer_thread()->OnReceivedLongPollIntervalUpdate(poll);
+  UseMockDelayProvider();
+
+  const TimeDelta backoff = TimeDelta::FromMilliseconds(100);
+
+  EXPECT_CALL(*syncer(), SyncShare(_))
+      .WillOnce(Invoke(sessions::test_util::SimulateCommitFailed))
+      .WillOnce(Invoke(sessions::test_util::SimulateCommitFailed))
+      .WillRepeatedly(DoAll(Invoke(sessions::test_util::SimulateSuccess),
+          RecordSyncShareAndPostSignal(&r, kMinNumSamples, this, &done)));
+  EXPECT_CALL(*delay(), GetDelay(_)).WillOnce(Return(backoff));
+
+  // Optimal start for the post-backoff poll party.
+  TimeTicks optimal_start = TimeTicks::Now() + poll + backoff;
+  syncer_thread()->Start(SyncerThread::NORMAL_MODE);
+  done.TimedWait(timeout());
+
+  // Check for healthy polling after backoff is relieved.
+  // Can't use AnalyzePollRun because first sync is a continuation. Bleh.
+  for (size_t i = 0; i < r.times.size(); i++) {
+    SCOPED_TRACE(testing::Message() << "SyncShare # (" << i << ")");
+    TimeTicks optimal_next_sync = optimal_start + poll * i;
+    EXPECT_GE(r.times[i], optimal_next_sync);
+    EXPECT_LT(r.times[i], optimal_next_sync + poll);
+    EXPECT_EQ(i == 0 ? GetUpdatesCallerInfo::SYNC_CYCLE_CONTINUATION
+                     : GetUpdatesCallerInfo::PERIODIC,
+              r.snapshots[i]->source.first);
+  }
+}
+
+TEST_F(SyncerThread2Test, GetRecommendedDelay) {
+  EXPECT_LE(TimeDelta::FromSeconds(0),
+            SyncerThread::GetRecommendedDelay(TimeDelta::FromSeconds(0)));
+  EXPECT_LE(TimeDelta::FromSeconds(1),
+            SyncerThread::GetRecommendedDelay(TimeDelta::FromSeconds(1)));
+  EXPECT_LE(TimeDelta::FromSeconds(50),
+            SyncerThread::GetRecommendedDelay(TimeDelta::FromSeconds(50)));
+  EXPECT_LE(TimeDelta::FromSeconds(10),
+            SyncerThread::GetRecommendedDelay(TimeDelta::FromSeconds(10)));
+  EXPECT_EQ(TimeDelta::FromSeconds(kMaxBackoffSeconds),
+            SyncerThread::GetRecommendedDelay(
+                TimeDelta::FromSeconds(kMaxBackoffSeconds)));
+  EXPECT_EQ(TimeDelta::FromSeconds(kMaxBackoffSeconds),
+            SyncerThread::GetRecommendedDelay(
+                TimeDelta::FromSeconds(kMaxBackoffSeconds + 1)));
+}
+
+// Test config tasks don't run during normal mode.
+// TODO(tim): Implement this test and then the functionality!
+TEST_F(SyncerThread2Test, DISABLED_NoConfigDuringNormal) {
+}
+
+// Test that starting the syncer thread without a valid connection doesn't
+// break things when a connection is detected.
+// Test config tasks don't run during normal mode.
+// TODO(tim): Implement this test and then the functionality!
+TEST_F(SyncerThread2Test, DISABLED_StartWhenNotConnected) {
+
+}
+
+}  // namespace s3
+}  // namespace browser_sync
+
+// SyncerThread won't outlive the test!
+DISABLE_RUNNABLE_METHOD_REFCOUNT(browser_sync::s3::SyncerThread2Test);
+