WIP: Towards NonBlockingTypeProcessorCore

sync/engine/non_blocking_type_processor_core_unittest.cc

Index: sync/engine/non_blocking_type_processor_core_unittest.cc
diff --git a/sync/engine/non_blocking_type_processor_core_unittest.cc b/sync/engine/non_blocking_type_processor_core_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0fdec932e3a02cf22ac8ea47dac1fc6201d1155c
--- /dev/null
+++ b/sync/engine/non_blocking_type_processor_core_unittest.cc
@@ -0,0 +1,859 @@
+// Copyright 2014 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 "sync/engine/non_blocking_type_processor_core.h"
+
+#include "base/basictypes.h"
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/callback.h"
+#include "sync/engine/non_blocking_sync_common.h"
+#include "sync/engine/non_blocking_type_commit_contribution.h"
+#include "sync/protocol/sync.pb.h"
+#include "sync/sessions/status_controller.h"
+#include "sync/syncable/syncable_util.h"
+#include "sync/util/time.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+using google::protobuf::RepeatedPtrField;
+
+namespace syncer {
+
+class NonBlockingTypeProcessorCoreTest;
+
+namespace {
+
+class MockNonBlockingTypeProcessor : public NonBlockingTypeProcessorInterface {
+ public:
+  MockNonBlockingTypeProcessor(NonBlockingTypeProcessorCoreTest* parent);
+  virtual ~MockNonBlockingTypeProcessor();
+
+  virtual void ReceiveCommitResponse(
+      const DataTypeState& type_state,
+      const CommitResponseDataList& response_list) OVERRIDE;
+  virtual void ReceiveUpdateResponse(
+      const DataTypeState& type_state,
+      const UpdateResponseDataList& response_list) OVERRIDE;
+
+ private:
+  NonBlockingTypeProcessorCoreTest* parent_;
+
+  DISALLOW_COPY_AND_ASSIGN(MockNonBlockingTypeProcessor);
+};
+
+}  // namespace
+
+// Tests the NonBlockingTypeProcessorCore.
+//
+// This class passes messages between the model thread and sync server.
+// As such, its code is subject to lots of different race conditions.  This
+// test harness lets us exhaustively test all possibl races.  We try to
+// focus on just a few interesting cases, though.
+//
+// Inputs:
+// - Initial data type state from the model thread.
+// - Commit requests from the model thread.
+// - Update responses from the server.
+// - Commit responses from the server.
+//
+// Outputs:
+// - Commit requests to the server.
+// - Commit responses to the model thread.
+// - Update responses to the model thread.
+//
+// We use the MockNonBlockingTypeProcessor to stub out all communication
+// with the model thread.  That interface is synchronous, which makes it
+// much easier to test races.
+//
+// The interface with the server already built around "pulling" data from this
+// class, so we don't have to mock out any of it.  We do wrap it with some
+// convenience functions to we can emulate server behavior, though.
+class NonBlockingTypeProcessorCoreTest : public ::testing::Test {
+ public:
+  static const std::string kTypeParentId;
+
+  NonBlockingTypeProcessorCoreTest();
+  virtual ~NonBlockingTypeProcessorCoreTest();
+
+  // One of these Initialize functions should be called at the beginning of
+  // each test.
+
+  // Initializes with no data type state.  We will be unable to perform any
+  // significant server action until we receive an update response that
+  // contains the type root node for this type.
+  void FirstInitialize();
+
+  // Initializes with some existing data type state.  Allows us to start
+  // committing items right away.
+  void NormalInitialize();
+
+  // Initialize with a custom initial DataTypeState.
+  void InitializeWithState(const DataTypeState& state);
+
+  // Modifications on the model thread that get sent to us.
+  void CommitRequest(const std::string& tag, const std::string& value);
+  void DeleteRequest(const std::string& tag);
+
+  // Pretends to receive update messages from the server.
+  void TypeRootUpdateFromServer();
+  void UpdateFromServer(int64 version_offset,
+                        const std::string& tag,
+                        const std::string& value);
+  void TombstoneFromServer(int64 version_offset, const std::string& tag);
+
+  // Callbacks from the mock processor.  Called when the core_ tries to send
+  // messages to its associated processor on the model thread.
+  void ModelThreadReceivesCommitResponse(
+      const DataTypeState& type_state,
+      const CommitResponseDataList& response_list);
+  void ModelThreadReceivesUpdateResponse(
+      const DataTypeState& type_state,
+      const UpdateResponseDataList& response_list);
+
+  // By default, this harness behaves as if all tasks posted to the model
+  // thread are executed immediately.  However, this is not necessarily true.
+  // The model's TaskRunner has a queue, and the tasks we post to it could
+  // linger there for a while.  In the meantime, the model thread could
+  // continue posting tasks to us based on its stale state.
+  //
+  // If you want to test those race cases, then these functions are for you.
+  void SetModelThreadIsSynchronous(bool is_synchronous);
+  void PumpModelThread();
+
+  // Returns true if the |core_| is ready to commit something.
+  bool WillCommit();
+
+  // Pretend to successfully commit all outstanding unsynced items.
+  // It is safe to call this only if WillCommit() returns true.
+  void DoSuccessfulCommit();
+
+  // Read commit messages the core_ sent to the emulated server.
+  size_t GetNumCommitMessagesOnServer() const;
+  sync_pb::ClientToServerMessage GetNthCommitMessageOnServer(size_t n) const;
+
+  // Read the latest version of sync entities committed to the emulated server.
+  bool HasCommitEntityOnServer(const std::string& tag) const;
+  sync_pb::SyncEntity GetLatestCommitEntityOnServer(
+      const std::string& tag) const;
+
+  // Read the latest update messages received on the model thread.
+  // Note that if the model thread is in non-blocking mode, this data will not
+  // be updated until the response is actually processed by the model thread.
+  size_t GetNumModelThreadUpdateResponses() const;
+  UpdateResponseDataList GetNthModelThreadUpdateResponse(size_t n) const;
+  DataTypeState GetNthModelThreadUpdateState(size_t n) const;
+
+  // Reads the latest update response datas on the model thread.
+  // Note that if the model thread is in non-blocking mode, this data will not
+  // be updated until the response is actually processed by the model thread.
+  bool HasUpdateResponseOnModelThread(const std::string& tag) const;
+  UpdateResponseData GetUpdateResponseOnModelThread(
+      const std::string& tag) const;
+
+  // Read the latest commit messages received on the model thread.
+  // Note that if the model thread is in non-blocking mode, this data will not
+  // be updated until the response is actually processed by the model thread.
+  size_t GetNumModelThreadCommitResponses() const;
+  CommitResponseDataList GetNthModelThreadCommitResponse(size_t n) const;
+  DataTypeState GetNthModelThreadCommitState(size_t n) const;
+
+  // Reads the latest commit response datas on the model thread.
+  // Note that if the model thread is in non-blocking mode, this data will not
+  // be updated until the response is actually processed by the model thread.
+  bool HasCommitResponseOnModelThread(const std::string& tag) const;
+  CommitResponseData GetCommitResponseOnModelThread(
+      const std::string& tag) const;
+
+  // Helpers for building various messages and structures.
+  std::string GenerateId(const std::string& tag_hash) const;
+  std::string GenerateTagHash(const std::string& tag) const;
+  sync_pb::EntitySpecifics GenerateSpecifics(const std::string& tag,
+                                             const std::string& value) const;
+
+  // Get and set our emulated server state.
+  int64 GetServerVersion(const std::string& tag_hash);
+  void SetServerVersion(const std::string& tag_hash, int64 version);
+
+  // Get and set our emulated model thread state.
+  int64 GetCurrentSequenceNumber(const std::string& tag_hash) const;
+  int64 GetNextSequenceNumber(const std::string& tag_hash);
+  int64 GetModelVersion(const std::string& tag_hash) const;
+  void SetModelVersion(const std::string& tag_hash, int64 version);
+
+  // Receive a commit response in the emulated model thread.
+  void ModelThreadReceiveCommitResponseImpl(
+      const DataTypeState& type_state,
+      const CommitResponseDataList& response_list);
+
+  // Receive an update response in the emulated model thread.
+  void ModelThreadReceiveUpdateResponseImpl(
+      const DataTypeState& type_state,
+      const UpdateResponseDataList& response_list);
+
+ private:
+  sync_pb::DataTypeProgressMarker GenerateResponseProgressMarker() const;
+
+  scoped_ptr<NonBlockingTypeProcessorCore> core_;
+  MockNonBlockingTypeProcessor* mock_processor_;
+
+  // Model thread state maps.
+  std::map<const std::string, int64> model_sequence_numbers_;
+  std::map<const std::string, int64> model_base_versions_;
+
+  // Server state maps.
+  std::map<const std::string, int64> server_versions_;
+
+  // Logs of messages sent to the server.  Used in assertions.
+  std::map<const std::string, sync_pb::SyncEntity> committed_items_;
+  std::vector<sync_pb::ClientToServerMessage> commit_messages_;
+
+  // State related to emulation of the model thread's task queue.  Used to
+  // defer model thread work to simulate a full model thread task runner queue.
+  bool model_thread_is_synchronous_;
+  std::vector<base::Closure> model_thread_tasks_;
+
+  // A cache of messages sent to the model thread.
+  std::vector<CommitResponseDataList> commit_responses_to_model_thread_;
+  std::vector<UpdateResponseDataList> updates_responses_to_model_thread_;
+  std::vector<DataTypeState> updates_states_to_model_thread_;
+  std::vector<DataTypeState> commit_states_to_model_thread_;
+
+  // A cache of the latest responses on the model thread, by client tag.
+  std::map<const std::string, CommitResponseData>
+      model_thread_commit_response_items_;
+  std::map<const std::string, UpdateResponseData>
+      model_thread_update_response_items_;
+};
+
+// These had to wait until the class definition of
+// NonBlockingTypeProcessorCoreTest
+MockNonBlockingTypeProcessor::MockNonBlockingTypeProcessor(
+    NonBlockingTypeProcessorCoreTest* parent)
+    : parent_(parent) {
+}
+
+MockNonBlockingTypeProcessor::~MockNonBlockingTypeProcessor() {
+}
+
+void MockNonBlockingTypeProcessor::ReceiveCommitResponse(
+    const DataTypeState& type_state,
+    const CommitResponseDataList& response_list) {
+  parent_->ModelThreadReceivesCommitResponse(type_state, response_list);
+}
+
+void MockNonBlockingTypeProcessor::ReceiveUpdateResponse(
+    const DataTypeState& type_state,
+    const UpdateResponseDataList& response_list) {
+  parent_->ModelThreadReceivesUpdateResponse(type_state, response_list);
+}
+
+const std::string NonBlockingTypeProcessorCoreTest::kTypeParentId =
+    "PrefsRootNodeID";
+
+NonBlockingTypeProcessorCoreTest::NonBlockingTypeProcessorCoreTest()
+    : model_thread_is_synchronous_(true) {
+}
+
+NonBlockingTypeProcessorCoreTest::~NonBlockingTypeProcessorCoreTest() {
+}
+
+void NonBlockingTypeProcessorCoreTest::FirstInitialize() {
+  DataTypeState initial_state;
+  initial_state.progress_marker.set_data_type_id(
+      GetSpecificsFieldNumberFromModelType(PREFERENCES));
+  initial_state.next_client_id = 0;
+
+  InitializeWithState(initial_state);
+}
+
+void NonBlockingTypeProcessorCoreTest::NormalInitialize() {
+  DataTypeState initial_state;
+  initial_state.progress_marker.set_data_type_id(
+      GetSpecificsFieldNumberFromModelType(PREFERENCES));
+  initial_state.progress_marker.set_token("some_saved_progress_token");
+
+  initial_state.next_client_id = 10;
+  initial_state.type_root_id = kTypeParentId;
+
+  InitializeWithState(initial_state);
+}
+
+void NonBlockingTypeProcessorCoreTest::InitializeWithState(
+    const DataTypeState& state) {
+  DCHECK(!core_);
+
+  // We don't get to own this interace.  The |core_| keeps a scoped_ptr to it.
+  mock_processor_ = new MockNonBlockingTypeProcessor(this);
+  scoped_ptr<NonBlockingTypeProcessorInterface> interface(mock_processor_);
+
+  core_.reset(
+      new NonBlockingTypeProcessorCore(PREFERENCES, state, interface.Pass()));
+}
+
+void NonBlockingTypeProcessorCoreTest::CommitRequest(const std::string& tag,
+                                                     const std::string& value) {
+  const std::string tag_hash = GenerateTagHash(tag);
+  const int64 base_version = GetModelVersion(tag_hash);
+
+  CommitRequestData data;
+
+  // Initial commits don't have IDs.  Everything else does.
+  if (base_version > 0) {
+    data.id = GenerateId(tag_hash);
+  }
+
+  data.client_tag_hash = tag_hash;
+  data.sequence_number = GetNextSequenceNumber(tag_hash);
+
+  data.base_version = base_version;
+  data.ctime = base::Time::UnixEpoch() + base::TimeDelta::FromDays(1);
+  data.mtime = data.ctime + base::TimeDelta::FromSeconds(base_version);
+  data.non_unique_name = tag;
+
+  data.deleted = false;
+  data.specifics = GenerateSpecifics(tag, value);
+
+  CommitRequestDataList list;
+  list.push_back(data);
+
+  core_->RequestCommits(list);
+}
+
+void NonBlockingTypeProcessorCoreTest::DeleteRequest(const std::string& tag) {
+  const std::string tag_hash = GenerateTagHash(tag);
+  const int64 base_version = GetModelVersion(tag_hash);
+  CommitRequestData data;
+
+  // Initial commits don't have IDs.  Everything else does.
+  // FIXME: But deletions don't have initial commits...
+  if (base_version > 0) {
+    data.id = GenerateId(tag_hash);
+  }
+
+  data.sequence_number = GetNextSequenceNumber(tag_hash);
+
+  data.base_version = base_version;
+  data.ctime = base::Time::UnixEpoch() + base::TimeDelta::FromDays(1);
+  data.mtime = data.ctime + base::TimeDelta::FromSeconds(base_version);
+  data.deleted = true;
+
+  CommitRequestDataList list;
+  list.push_back(data);
+
+  core_->RequestCommits(list);
+}
+
+void NonBlockingTypeProcessorCoreTest::TypeRootUpdateFromServer() {
+  sync_pb::SyncEntity entity;
+
+  entity.set_id_string(kTypeParentId);
+  entity.set_parent_id_string("r");
+  entity.set_version(1000);
+  entity.set_ctime(TimeToProtoTime(base::Time::UnixEpoch()));
+  entity.set_mtime(TimeToProtoTime(base::Time::UnixEpoch()));
+  entity.set_server_defined_unique_tag(ModelTypeToRootTag(PREFERENCES));
+  entity.set_deleted(false);
+  AddDefaultFieldValue(PREFERENCES, entity.mutable_specifics());
+
+  const sync_pb::DataTypeProgressMarker& progress =
+      GenerateResponseProgressMarker();
+  const sync_pb::DataTypeContext blank_context;
+  sessions::StatusController dummy_status;
+
+  SyncEntityList entity_list;
+  entity_list.push_back(&entity);
+
+  core_->ProcessGetUpdatesResponse(
+      progress, blank_context, entity_list, &dummy_status);
+  core_->ApplyUpdates(&dummy_status);
+}
+
+void NonBlockingTypeProcessorCoreTest::UpdateFromServer(
+    int64 version_offset,
+    const std::string& tag,
+    const std::string& value) {
+  const std::string tag_hash = GenerateTagHash(tag);
+
+  int64 old_version = GetServerVersion(tag_hash);
+  int64 version = old_version + version_offset;
+  if (version > old_version) {
+    SetServerVersion(tag_hash, version);
+  }
+
+  sync_pb::SyncEntity entity;
+
+  entity.set_id_string(GenerateId(tag_hash));
+  entity.set_parent_id_string(kTypeParentId);
+  entity.set_version(version);
+
+  base::Time ctime = base::Time::UnixEpoch() + base::TimeDelta::FromDays(1);
+  base::Time mtime = ctime + base::TimeDelta::FromSeconds(version);
+  entity.set_ctime(TimeToProtoTime(ctime));
+  entity.set_mtime(TimeToProtoTime(mtime));
+
+  entity.set_client_defined_unique_tag(GenerateTagHash(tag));
+  entity.set_deleted(false);
+  entity.mutable_specifics()->CopyFrom(GenerateSpecifics(tag, value));
+
+  SyncEntityList entity_list;
+  entity_list.push_back(&entity);
+
+  const sync_pb::DataTypeProgressMarker& progress =
+      GenerateResponseProgressMarker();
+  const sync_pb::DataTypeContext blank_context;
+  sessions::StatusController dummy_status;
+
+  core_->ProcessGetUpdatesResponse(
+      progress, blank_context, entity_list, &dummy_status);
+  core_->ApplyUpdates(&dummy_status);
+}
+
+void NonBlockingTypeProcessorCoreTest::TombstoneFromServer(
+    int64 version_offset,
+    const std::string& tag) {
+  const std::string tag_hash = GenerateTagHash(tag);
+  int64 old_version = GetServerVersion(tag_hash);
+  int64 version = old_version + version_offset;
+  if (version > old_version) {
+    SetServerVersion(tag_hash, version);
+  }
+
+  UpdateResponseData data;
+
+  data.id = GenerateId(tag_hash);
+  data.client_tag_hash = tag_hash;
+  data.response_version = version;
+  data.ctime = base::Time::UnixEpoch() + base::TimeDelta::FromDays(1);
+  data.mtime = data.ctime + base::TimeDelta::FromSeconds(version);
+  data.non_unique_name = tag;
+  data.deleted = true;
+}
+
+void NonBlockingTypeProcessorCoreTest::ModelThreadReceivesCommitResponse(
+    const DataTypeState& type_state,
+    const CommitResponseDataList& response_list) {
+  base::Closure task = base::Bind(
+      &NonBlockingTypeProcessorCoreTest::ModelThreadReceiveCommitResponseImpl,
+      base::Unretained(this),
+      type_state,
+      response_list);
+  model_thread_tasks_.push_back(task);
+  if (model_thread_is_synchronous_)
+    PumpModelThread();
+}
+
+void NonBlockingTypeProcessorCoreTest::ModelThreadReceivesUpdateResponse(
+    const DataTypeState& type_state,
+    const UpdateResponseDataList& response_list) {
+  base::Closure task = base::Bind(
+      &NonBlockingTypeProcessorCoreTest::ModelThreadReceiveUpdateResponseImpl,
+      base::Unretained(this),
+      type_state,
+      response_list);
+  model_thread_tasks_.push_back(task);
+  if (model_thread_is_synchronous_)
+    PumpModelThread();
+}
+
+void NonBlockingTypeProcessorCoreTest::SetModelThreadIsSynchronous(
+    bool is_synchronous) {
+  model_thread_is_synchronous_ = is_synchronous;
+}
+
+void NonBlockingTypeProcessorCoreTest::PumpModelThread() {
+  for (std::vector<base::Closure>::iterator it = model_thread_tasks_.begin();
+       it != model_thread_tasks_.end();
+       ++it) {
+    it->Run();
+  }
+  model_thread_tasks_.clear();
+}
+
+bool NonBlockingTypeProcessorCoreTest::WillCommit() {
+  scoped_ptr<CommitContribution> contribution(core_->GetContribution(INT_MAX));
+
+  if (contribution) {
+    contribution->CleanUp();  // Gracefully abort the commit.
+    return true;
+  } else {
+    return false;
+  }
+}
+
+// Conveniently, this is all one big synchronous operation.  The sync thread
+// remains blocked while the commit is in progress, so we don't need to worry
+// about other tasks being run between the time when the commit request is
+// issued and the time when the commit response is received.
+void NonBlockingTypeProcessorCoreTest::DoSuccessfulCommit() {
+  DCHECK(WillCommit());
+  scoped_ptr<CommitContribution> contribution(core_->GetContribution(INT_MAX));
+
+  sync_pb::ClientToServerMessage message;
+  contribution->AddToCommitMessage(&message);
+  commit_messages_.push_back(message);
+
+  sync_pb::ClientToServerResponse response;
+  sync_pb::CommitResponse* commit_response = response.mutable_commit();
+
+  const RepeatedPtrField<sync_pb::SyncEntity>& entries =
+      message.commit().entries();
+  for (RepeatedPtrField<sync_pb::SyncEntity>::const_iterator it =
+           entries.begin();
+       it != entries.end();
+       ++it) {
+    const std::string tag_hash = it->client_defined_unique_tag();
+
+    committed_items_[tag_hash] = *it;
+
+    // Every commit increments the version number.
+    int64 version = GetServerVersion(tag_hash); version++;
+    SetServerVersion(tag_hash, version);
+
+    sync_pb::CommitResponse_EntryResponse* entryresponse =
+        commit_response->add_entryresponse();
+    entryresponse->set_response_type(sync_pb::CommitResponse::SUCCESS);
+    entryresponse->set_id_string(GenerateId(tag_hash));
+    entryresponse->set_parent_id_string(it->parent_id_string());
+    entryresponse->set_version(version);
+    entryresponse->set_name(it->name());
+    entryresponse->set_mtime(it->mtime());
+  }
+
+  sessions::StatusController dummy_status;
+  contribution->ProcessCommitResponse(response, &dummy_status);
+  contribution->CleanUp();
+}
+
+size_t NonBlockingTypeProcessorCoreTest::GetNumCommitMessagesOnServer() const {
+  return commit_messages_.size();
+}
+
+sync_pb::ClientToServerMessage
+NonBlockingTypeProcessorCoreTest::GetNthCommitMessageOnServer(size_t n) const {
+  DCHECK_LT(n, GetNumCommitMessagesOnServer());
+  return commit_messages_[n];
+}
+
+bool NonBlockingTypeProcessorCoreTest::HasCommitEntityOnServer(
+    const std::string& tag) const {
+  const std::string tag_hash = GenerateTagHash(tag);
+  std::map<const std::string, sync_pb::SyncEntity>::const_iterator it =
+      committed_items_.find(tag_hash);
+  return it != committed_items_.end();
+}
+
+sync_pb::SyncEntity
+NonBlockingTypeProcessorCoreTest::GetLatestCommitEntityOnServer(
+    const std::string& tag) const {
+  DCHECK(HasCommitEntityOnServer(tag));
+  const std::string tag_hash = GenerateTagHash(tag);
+  std::map<const std::string, sync_pb::SyncEntity>::const_iterator it =
+      committed_items_.find(tag_hash);
+  return it->second;
+}
+
+size_t NonBlockingTypeProcessorCoreTest::GetNumModelThreadUpdateResponses()
+    const {
+  return updates_responses_to_model_thread_.size();
+}
+
+UpdateResponseDataList
+NonBlockingTypeProcessorCoreTest::GetNthModelThreadUpdateResponse(
+    size_t n) const {
+  DCHECK(GetNumModelThreadUpdateResponses());
+  return updates_responses_to_model_thread_[n];
+}
+
+DataTypeState NonBlockingTypeProcessorCoreTest::GetNthModelThreadUpdateState(
+    size_t n) const {
+  DCHECK(GetNumModelThreadUpdateResponses());
+  return updates_states_to_model_thread_[n];
+}
+
+bool NonBlockingTypeProcessorCoreTest::HasUpdateResponseOnModelThread(
+    const std::string& tag) const {
+  const std::string tag_hash = GenerateTagHash(tag);
+  std::map<const std::string, UpdateResponseData>::const_iterator it =
+      model_thread_update_response_items_.find(tag_hash);
+  return it != model_thread_update_response_items_.end();
+}
+
+UpdateResponseData
+NonBlockingTypeProcessorCoreTest::GetUpdateResponseOnModelThread(
+    const std::string& tag) const {
+  const std::string tag_hash = GenerateTagHash(tag);
+  DCHECK(HasUpdateResponseOnModelThread(tag_hash));
+  std::map<const std::string, UpdateResponseData>::const_iterator it =
+      model_thread_update_response_items_.find(tag_hash);
+  return it->second;
+}
+
+size_t NonBlockingTypeProcessorCoreTest::GetNumModelThreadCommitResponses()
+    const {
+  return commit_responses_to_model_thread_.size();
+}
+
+CommitResponseDataList
+NonBlockingTypeProcessorCoreTest::GetNthModelThreadCommitResponse(
+    size_t n) const {
+  DCHECK(GetNumModelThreadCommitResponses());
+  return commit_responses_to_model_thread_[n];
+}
+
+DataTypeState NonBlockingTypeProcessorCoreTest::GetNthModelThreadCommitState(
+    size_t n) const {
+  DCHECK(GetNumModelThreadCommitResponses());
+  return commit_states_to_model_thread_[n];
+}
+
+std::string NonBlockingTypeProcessorCoreTest::GenerateId(
+    const std::string& tag_hash) const {
+  return "FakeId:" + tag_hash;
+}
+
+bool NonBlockingTypeProcessorCoreTest::HasCommitResponseOnModelThread(
+    const std::string& tag) const {
+  const std::string tag_hash = GenerateTagHash(tag);
+  std::map<const std::string, CommitResponseData>::const_iterator it =
+      model_thread_commit_response_items_.find(tag_hash);
+  return it != model_thread_commit_response_items_.end();
+}
+
+CommitResponseData
+NonBlockingTypeProcessorCoreTest::GetCommitResponseOnModelThread(
+    const std::string& tag) const {
+  DCHECK(HasCommitResponseOnModelThread(tag));
+  const std::string tag_hash = GenerateTagHash(tag);
+  std::map<const std::string, CommitResponseData>::const_iterator it =
+      model_thread_commit_response_items_.find(tag_hash);
+  return it->second;
+}
+
+std::string NonBlockingTypeProcessorCoreTest::GenerateTagHash(
+    const std::string& tag) const {
+  const std::string& client_tag_hash =
+      syncable::GenerateSyncableHash(PREFERENCES, tag);
+
+  return client_tag_hash;
+}
+
+sync_pb::EntitySpecifics NonBlockingTypeProcessorCoreTest::GenerateSpecifics(
+    const std::string& tag,
+    const std::string& value) const {
+  sync_pb::EntitySpecifics specifics;
+  specifics.mutable_preference()->set_name(tag);
+  specifics.mutable_preference()->set_value(value);
+  return specifics;
+}
+
+int64 NonBlockingTypeProcessorCoreTest::GetServerVersion(
+    const std::string& tag_hash) {
+  std::map<const std::string, int64>::const_iterator it;
+  it = server_versions_.find(tag_hash);
+  if (it == server_versions_.end()) {
+    return 0;
+  } else {
+    return it->second;
+  }
+}
+
+void NonBlockingTypeProcessorCoreTest::SetServerVersion(const std::string& tag_hash,
+                                                        int64 version) {
+  server_versions_[tag_hash] = version;
+}
+
+// Fetches the sequence number as of the most recent update request.
+int64 NonBlockingTypeProcessorCoreTest::GetCurrentSequenceNumber(
+    const std::string& tag_hash) const {
+  std::map<const std::string, int64>::const_iterator it =
+      model_sequence_numbers_.find(tag_hash);
+  if (it == model_sequence_numbers_.end()) {
+    return 0;
+  } else {
+    return it->second;
+  }
+}
+
+// The model thread should be sending us items with strictly increasing
+// sequence numbers.  Here's where we emulate that behavior.
+int64 NonBlockingTypeProcessorCoreTest::GetNextSequenceNumber(
+    const std::string& tag_hash) {
+  int64 sequence_number = GetCurrentSequenceNumber(tag_hash);
+  sequence_number++;
+  model_sequence_numbers_[tag_hash] = sequence_number;
+  return sequence_number;
+}
+
+// Fetches the model's base version.
+int64 NonBlockingTypeProcessorCoreTest::GetModelVersion(
+    const std::string& tag_hash) const {
+  std::map<const std::string, int64>::const_iterator it =
+      model_base_versions_.find(tag_hash);
+  if (it == model_base_versions_.end()) {
+    return 0;
+  } else {
+    return it->second;
+  }
+}
+
+void NonBlockingTypeProcessorCoreTest::SetModelVersion(const std::string& tag_hash,
+                                                       int64 version) {
+  model_base_versions_[tag_hash] = version;
+}
+
+void NonBlockingTypeProcessorCoreTest::ModelThreadReceiveCommitResponseImpl(
+    const DataTypeState& type_state,
+    const CommitResponseDataList& response_list) {
+  commit_responses_to_model_thread_.push_back(response_list);
+  commit_states_to_model_thread_.push_back(type_state);
+  for (CommitResponseDataList::const_iterator it = response_list.begin();
+       it != response_list.end();
+       ++it) {
+    model_thread_commit_response_items_.insert(std::make_pair(it->client_tag_hash, *it));
+
+    // Server wins.  Set the model's base version.
+    SetModelVersion(it->client_tag_hash, it->response_version);
+  }
+}
+
+void NonBlockingTypeProcessorCoreTest::ModelThreadReceiveUpdateResponseImpl(
+    const DataTypeState& type_state,
+    const UpdateResponseDataList& response_list) {
+  updates_responses_to_model_thread_.push_back(response_list);
+  updates_states_to_model_thread_.push_back(type_state);
+  for (UpdateResponseDataList::const_iterator it = response_list.begin();
+       it != response_list.end();
+       ++it) {
+    model_thread_update_response_items_.insert(std::make_pair(it->client_tag_hash, *it));
+
+    // Server wins.  Set the model's base version.
+    SetModelVersion(it->client_tag_hash, it->response_version);
+  }
+}
+
+sync_pb::DataTypeProgressMarker
+NonBlockingTypeProcessorCoreTest::GenerateResponseProgressMarker() const {
+  sync_pb::DataTypeProgressMarker progress;
+  progress.set_data_type_id(PREFERENCES);
+  progress.set_token("non_null_progress_token");
+  return progress;
+}
+
+// Requests a commit and verifies the messages sent to the client and server as
+// a result.
+//
+// This test performs sanity checks on most of the fields in these messages.
+// For the most part this is checking that the test code behaves as expected
+// and the |core_| doesn't mess up its simple task of moving around these
+// values.  It makes sense to have one or two tests that are this thorough, but
+// we shouldn't be this verbose in all tests.
+TEST_F(NonBlockingTypeProcessorCoreTest, SimpleCommit) {
+  NormalInitialize();
+
+  EXPECT_FALSE(WillCommit());
+  EXPECT_EQ(0U, GetNumCommitMessagesOnServer());
+  EXPECT_EQ(0U, GetNumModelThreadCommitResponses());
+
+  CommitRequest("tag1", "value1");
+
+  ASSERT_TRUE(WillCommit());
+  DoSuccessfulCommit();
+
+  const std::string& client_tag_hash = GenerateTagHash("tag1");
+
+  // Exhaustively verify the SyncEntity sent in the commit message.
+  ASSERT_EQ(1U, GetNumCommitMessagesOnServer());
+  EXPECT_EQ(1, GetNthCommitMessageOnServer(0).commit().entries_size());
+  ASSERT_TRUE(HasCommitEntityOnServer("tag1"));
+  const sync_pb::SyncEntity& entity = GetLatestCommitEntityOnServer("tag1");
+  EXPECT_FALSE(entity.id_string().empty());
+  EXPECT_EQ(kTypeParentId, entity.parent_id_string());
+  EXPECT_EQ(entity.version(), 0);
+  EXPECT_NE(0, entity.mtime());
+  EXPECT_NE(0, entity.ctime());
+  EXPECT_EQ("tag1", entity.name());
+  EXPECT_EQ(client_tag_hash, entity.client_defined_unique_tag());
+  EXPECT_EQ("tag1", entity.specifics().preference().name());
+  EXPECT_EQ("value1", entity.specifics().preference().value());
+
+  // Exhaustively verify the commit response returned to the model thread.
+  ASSERT_EQ(1U, GetNumModelThreadCommitResponses());
+  EXPECT_EQ(1U, GetNthModelThreadCommitResponse(0).size());
+  ASSERT_TRUE(HasCommitResponseOnModelThread("tag1"));
+  const CommitResponseData& commit_response =
+      GetCommitResponseOnModelThread("tag1");
+
+  // The ID changes in a commit response to initial commit.
+  EXPECT_FALSE(commit_response.id.empty());
+  EXPECT_NE(entity.id_string(), commit_response.id);
+
+  EXPECT_EQ(client_tag_hash, commit_response.client_tag_hash);
+  EXPECT_EQ(GetCurrentSequenceNumber(client_tag_hash),
+            commit_response.sequence_number);
+  EXPECT_LT(0, commit_response.response_version);
+}
+
+TEST_F(NonBlockingTypeProcessorCoreTest, NoCommitUntilFirstUpdate) {
+  FirstInitialize();  // Initialize with no saved sync state.
+
+  CommitRequest("tag1", "value1");
+  EXPECT_FALSE(WillCommit());
+
+  // Receive an update response that contains only the type root node.
+  TypeRootUpdateFromServer();
+
+  EXPECT_TRUE(WillCommit());
+
+  // The type root node itself should not be sent to the model thread.
+  // However, we will still generate and send a message to the model
+  // thread to update its DataTypeState with the new information.
+  // (specifically the parent ID) so we won't have to fetch it again
+  // on the next restart.
+  ASSERT_EQ(1U, GetNumModelThreadUpdateResponses());
+  EXPECT_EQ(0U, GetNthModelThreadUpdateResponse(0).size());
+  const DataTypeState& state = GetNthModelThreadUpdateState(0);
+  EXPECT_FALSE(state.progress_marker.token().empty());
+  EXPECT_FALSE(state.type_root_id.empty());
+}
+
+// Commit two new entities in two separate commit messages.
+TEST_F(NonBlockingTypeProcessorCoreTest, TwoNewItemsCommittedSeparately) {
+  NormalInitialize();
+
+  // Commit the first of two entities.
+  CommitRequest("tag1", "value1");
+  ASSERT_TRUE(WillCommit());
+  DoSuccessfulCommit();
+  ASSERT_EQ(1U, GetNumCommitMessagesOnServer());
+  EXPECT_EQ(1, GetNthCommitMessageOnServer(0).commit().entries_size());
+  ASSERT_TRUE(HasCommitEntityOnServer("tag1"));
+  const sync_pb::SyncEntity& tag1_entity =
+      GetLatestCommitEntityOnServer("tag1");
+
+  // Commit the second of two entities.
+  CommitRequest("tag2", "value2");
+  ASSERT_TRUE(WillCommit());
+  DoSuccessfulCommit();
+  ASSERT_EQ(2U, GetNumCommitMessagesOnServer());
+  EXPECT_EQ(1, GetNthCommitMessageOnServer(1).commit().entries_size());
+  ASSERT_TRUE(HasCommitEntityOnServer("tag2"));
+  const sync_pb::SyncEntity& tag2_entity =
+      GetLatestCommitEntityOnServer("tag2");
+
+  EXPECT_FALSE(WillCommit());
+
+  // The IDs assigned by the |core_| should be unique.
+  EXPECT_NE(tag1_entity.id_string(), tag2_entity.id_string());
+
+  // Check that the committed specifics values are sane.
+  EXPECT_EQ(tag1_entity.specifics().preference().value(), "value1");
+  EXPECT_EQ(tag2_entity.specifics().preference().value(), "value2");
+
+  // There should have been two separate commit responses sent to the model
+  // thread.  They should be uninteresting, so we don't bother inspecting them.
+  EXPECT_EQ(2U, GetNumModelThreadCommitResponses());
+}
+
+}  // namespace syncer