src/base/prefs/json_pref_store_unittest.cc - cobalt - Git at Google

 // Copyright (c) 2012 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/prefs/json_pref_store.h"

 #include "base/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/path_service.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "base/threading/thread.h"
 #include "base/utf_string_conversions.h"
 #include "base/values.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"

 namespace base {
 namespace {

 const char kHomePage[] = "homepage";

 class MockPrefStoreObserver : public PrefStore::Observer {
  public:
   MOCK_METHOD1(OnPrefValueChanged, void (const std::string&));
   MOCK_METHOD1(OnInitializationCompleted, void (bool));
 };

 class MockReadErrorDelegate : public PersistentPrefStore::ReadErrorDelegate {
  public:
   MOCK_METHOD1(OnError, void(PersistentPrefStore::PrefReadError));
 };

 }  // namespace

 class JsonPrefStoreTest : public testing::Test {
  protected:
   virtual void SetUp() override {
     ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());

     ASSERT_TRUE(PathService::Get(base::DIR_SOURCE_ROOT, &data_dir_));
     data_dir_ = data_dir_.AppendASCII("base");
     data_dir_ = data_dir_.AppendASCII("prefs");
     data_dir_ = data_dir_.AppendASCII("test");
     data_dir_ = data_dir_.AppendASCII("data");
     data_dir_ = data_dir_.AppendASCII("pref_service");
     LOG(WARNING) << data_dir_.value().c_str();
     ASSERT_TRUE(file_util::PathExists(data_dir_));
   }

   // The path to temporary directory used to contain the test operations.
   base::ScopedTempDir temp_dir_;
   // The path to the directory where the test data is stored.
   FilePath data_dir_;
   // A message loop that we can use as the file thread message loop.
   MessageLoop message_loop_;
 };

 // Test fallback behavior for a nonexistent file.
 TEST_F(JsonPrefStoreTest, NonExistentFile) {
   FilePath bogus_input_file = data_dir_.AppendASCII("read.txt");
   ASSERT_FALSE(file_util::PathExists(bogus_input_file));
   scoped_refptr<JsonPrefStore> pref_store =
       new JsonPrefStore(
           bogus_input_file, message_loop_.message_loop_proxy());
   EXPECT_EQ(PersistentPrefStore::PREF_READ_ERROR_NO_FILE,
             pref_store->ReadPrefs());
   EXPECT_FALSE(pref_store->ReadOnly());
 }

 // Test fallback behavior for an invalid file.
 TEST_F(JsonPrefStoreTest, InvalidFile) {
   FilePath invalid_file_original = data_dir_.AppendASCII("invalid.json");
   FilePath invalid_file = temp_dir_.path().AppendASCII("invalid.json");
   ASSERT_TRUE(file_util::CopyFile(invalid_file_original, invalid_file));
   scoped_refptr<JsonPrefStore> pref_store =
       new JsonPrefStore(
           invalid_file, message_loop_.message_loop_proxy());
   EXPECT_EQ(PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE,
             pref_store->ReadPrefs());
   EXPECT_FALSE(pref_store->ReadOnly());

   // The file should have been moved aside.
   EXPECT_FALSE(file_util::PathExists(invalid_file));
   FilePath moved_aside = temp_dir_.path().AppendASCII("invalid.bad");
   EXPECT_TRUE(file_util::PathExists(moved_aside));
   EXPECT_TRUE(file_util::TextContentsEqual(invalid_file_original,
                                            moved_aside));
 }

 // This function is used to avoid code duplication while testing synchronous and
 // asynchronous version of the JsonPrefStore loading.
 void RunBasicJsonPrefStoreTest(JsonPrefStore* pref_store,
                                const FilePath& output_file,
                                const FilePath& golden_output_file) {
   const char kNewWindowsInTabs[] = "tabs.new_windows_in_tabs";
   const char kMaxTabs[] = "tabs.max_tabs";
   const char kLongIntPref[] = "long_int.pref";

   std::string cnn("http://www.cnn.com");

   const Value* actual;
   EXPECT_TRUE(pref_store->GetValue(kHomePage, &actual));
   std::string string_value;
   EXPECT_TRUE(actual->GetAsString(&string_value));
   EXPECT_EQ(cnn, string_value);

   const char kSomeDirectory[] = "some_directory";

   EXPECT_TRUE(pref_store->GetValue(kSomeDirectory, &actual));
   FilePath::StringType path;
   EXPECT_TRUE(actual->GetAsString(&path));
   EXPECT_EQ(FilePath::StringType(FILE_PATH_LITERAL("/usr/local/")), path);
   FilePath some_path(FILE_PATH_LITERAL("/usr/sbin/"));

   pref_store->SetValue(kSomeDirectory, new StringValue(some_path.value()));
   EXPECT_TRUE(pref_store->GetValue(kSomeDirectory, &actual));
   EXPECT_TRUE(actual->GetAsString(&path));
   EXPECT_EQ(some_path.value(), path);

   // Test reading some other data types from sub-dictionaries.
   EXPECT_TRUE(pref_store->GetValue(kNewWindowsInTabs, &actual));
   bool boolean = false;
   EXPECT_TRUE(actual->GetAsBoolean(&boolean));
   EXPECT_TRUE(boolean);

   pref_store->SetValue(kNewWindowsInTabs, new FundamentalValue(false));
   EXPECT_TRUE(pref_store->GetValue(kNewWindowsInTabs, &actual));
   EXPECT_TRUE(actual->GetAsBoolean(&boolean));
   EXPECT_FALSE(boolean);

   EXPECT_TRUE(pref_store->GetValue(kMaxTabs, &actual));
   int integer = 0;
   EXPECT_TRUE(actual->GetAsInteger(&integer));
   EXPECT_EQ(20, integer);
   pref_store->SetValue(kMaxTabs, new FundamentalValue(10));
   EXPECT_TRUE(pref_store->GetValue(kMaxTabs, &actual));
   EXPECT_TRUE(actual->GetAsInteger(&integer));
   EXPECT_EQ(10, integer);

   pref_store->SetValue(kLongIntPref,
                        new StringValue(base::Int64ToString(214748364842LL)));
   EXPECT_TRUE(pref_store->GetValue(kLongIntPref, &actual));
   EXPECT_TRUE(actual->GetAsString(&string_value));
   int64 value;
   base::StringToInt64(string_value, &value);
   EXPECT_EQ(214748364842LL, value);

   // Serialize and compare to expected output.
   ASSERT_TRUE(file_util::PathExists(golden_output_file));
   pref_store->CommitPendingWrite();
   MessageLoop::current()->RunUntilIdle();
   EXPECT_TRUE(file_util::TextContentsEqual(golden_output_file, output_file));
   ASSERT_TRUE(file_util::Delete(output_file, false));
 }

 TEST_F(JsonPrefStoreTest, Basic) {
   ASSERT_TRUE(file_util::CopyFile(data_dir_.AppendASCII("read.json"),
                                   temp_dir_.path().AppendASCII("write.json")));

   // Test that the persistent value can be loaded.
   FilePath input_file = temp_dir_.path().AppendASCII("write.json");
   ASSERT_TRUE(file_util::PathExists(input_file));
   scoped_refptr<JsonPrefStore> pref_store =
       new JsonPrefStore(
           input_file, message_loop_.message_loop_proxy());
   ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_NONE, pref_store->ReadPrefs());
   ASSERT_FALSE(pref_store->ReadOnly());

   // The JSON file looks like this:
   // {
   //   "homepage": "http://www.cnn.com",
   //   "some_directory": "/usr/local/",
   //   "tabs": {
   //     "new_windows_in_tabs": true,
   //     "max_tabs": 20
   //   }
   // }

   RunBasicJsonPrefStoreTest(pref_store,
                             input_file,
                             data_dir_.AppendASCII("write.golden.json"));
 }

 TEST_F(JsonPrefStoreTest, BasicAsync) {
   ASSERT_TRUE(file_util::CopyFile(data_dir_.AppendASCII("read.json"),
                                   temp_dir_.path().AppendASCII("write.json")));

   // Test that the persistent value can be loaded.
   FilePath input_file = temp_dir_.path().AppendASCII("write.json");
   ASSERT_TRUE(file_util::PathExists(input_file));
   scoped_refptr<JsonPrefStore> pref_store =
       new JsonPrefStore(
           input_file, message_loop_.message_loop_proxy());

   {
     MockPrefStoreObserver mock_observer;
     pref_store->AddObserver(&mock_observer);

     MockReadErrorDelegate* mock_error_delegate = new MockReadErrorDelegate;
     pref_store->ReadPrefsAsync(mock_error_delegate);

     EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(1);
     EXPECT_CALL(*mock_error_delegate,
                 OnError(PersistentPrefStore::PREF_READ_ERROR_NONE)).Times(0);
     message_loop_.RunUntilIdle();
     pref_store->RemoveObserver(&mock_observer);

     ASSERT_FALSE(pref_store->ReadOnly());
   }

   // The JSON file looks like this:
   // {
   //   "homepage": "http://www.cnn.com",
   //   "some_directory": "/usr/local/",
   //   "tabs": {
   //     "new_windows_in_tabs": true,
   //     "max_tabs": 20
   //   }
   // }

   RunBasicJsonPrefStoreTest(pref_store,
                             input_file,
                             data_dir_.AppendASCII("write.golden.json"));
 }

 // Tests asynchronous reading of the file when there is no file.
 TEST_F(JsonPrefStoreTest, AsyncNonExistingFile) {
   FilePath bogus_input_file = data_dir_.AppendASCII("read.txt");
   ASSERT_FALSE(file_util::PathExists(bogus_input_file));
   scoped_refptr<JsonPrefStore> pref_store =
       new JsonPrefStore(
           bogus_input_file, message_loop_.message_loop_proxy());
   MockPrefStoreObserver mock_observer;
   pref_store->AddObserver(&mock_observer);

   MockReadErrorDelegate *mock_error_delegate = new MockReadErrorDelegate;
   pref_store->ReadPrefsAsync(mock_error_delegate);

   EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(1);
   EXPECT_CALL(*mock_error_delegate,
               OnError(PersistentPrefStore::PREF_READ_ERROR_NO_FILE)).Times(1);
   message_loop_.RunUntilIdle();
   pref_store->RemoveObserver(&mock_observer);

   EXPECT_FALSE(pref_store->ReadOnly());
 }

 TEST_F(JsonPrefStoreTest, NeedsEmptyValue) {
   FilePath pref_file = temp_dir_.path().AppendASCII("write.json");

   ASSERT_TRUE(file_util::CopyFile(
       data_dir_.AppendASCII("read.need_empty_value.json"),
       pref_file));

   // Test that the persistent value can be loaded.
   ASSERT_TRUE(file_util::PathExists(pref_file));
   scoped_refptr<JsonPrefStore> pref_store =
       new JsonPrefStore(
           pref_file, message_loop_.message_loop_proxy());
   ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_NONE, pref_store->ReadPrefs());
   ASSERT_FALSE(pref_store->ReadOnly());

   // The JSON file looks like this:
   // {
   //   "list": [ 1 ],
   //   "list_needs_empty_value": [ 2 ],
   //   "dict": {
   //     "dummy": true,
   //   },
   //   "dict_needs_empty_value": {
   //     "dummy": true,
   //   },
   // }

   // Set flag to preserve empty values for the following keys.
   pref_store->MarkNeedsEmptyValue("list_needs_empty_value");
   pref_store->MarkNeedsEmptyValue("dict_needs_empty_value");

   // Set all keys to empty values.
   pref_store->SetValue("list", new base::ListValue);
   pref_store->SetValue("list_needs_empty_value", new base::ListValue);
   pref_store->SetValue("dict", new base::DictionaryValue);
   pref_store->SetValue("dict_needs_empty_value", new base::DictionaryValue);

   // Write to file.
   pref_store->CommitPendingWrite();
   MessageLoop::current()->RunUntilIdle();

   // Compare to expected output.
   FilePath golden_output_file =
       data_dir_.AppendASCII("write.golden.need_empty_value.json");
   ASSERT_TRUE(file_util::PathExists(golden_output_file));
   EXPECT_TRUE(file_util::TextContentsEqual(golden_output_file, pref_file));
 }

 }  // namespace base
	// Copyright (c) 2012 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/prefs/json_pref_store.h"

	#include "base/file_util.h"
	#include "base/files/scoped_temp_dir.h"
	#include "base/memory/ref_counted.h"
	#include "base/memory/scoped_ptr.h"
	#include "base/path_service.h"
	#include "base/string_number_conversions.h"
	#include "base/string_util.h"
	#include "base/threading/sequenced_worker_pool.h"
	#include "base/threading/thread.h"
	#include "base/utf_string_conversions.h"
	#include "base/values.h"
	#include "testing/gmock/include/gmock/gmock.h"
	#include "testing/gtest/include/gtest/gtest.h"

	namespace base {
	namespace {

	const char kHomePage[] = "homepage";

	class MockPrefStoreObserver : public PrefStore::Observer {
	public:
	MOCK_METHOD1(OnPrefValueChanged, void (const std::string&));
	MOCK_METHOD1(OnInitializationCompleted, void (bool));
	};

	class MockReadErrorDelegate : public PersistentPrefStore::ReadErrorDelegate {
	public:
	MOCK_METHOD1(OnError, void(PersistentPrefStore::PrefReadError));
	};

	} // namespace

	class JsonPrefStoreTest : public testing::Test {
	protected:
	virtual void SetUp() override {
	ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());

	ASSERT_TRUE(PathService::Get(base::DIR_SOURCE_ROOT, &data_dir_));
	data_dir_ = data_dir_.AppendASCII("base");
	data_dir_ = data_dir_.AppendASCII("prefs");
	data_dir_ = data_dir_.AppendASCII("test");
	data_dir_ = data_dir_.AppendASCII("data");
	data_dir_ = data_dir_.AppendASCII("pref_service");
	LOG(WARNING) << data_dir_.value().c_str();
	ASSERT_TRUE(file_util::PathExists(data_dir_));
	}

	// The path to temporary directory used to contain the test operations.
	base::ScopedTempDir temp_dir_;
	// The path to the directory where the test data is stored.
	FilePath data_dir_;
	// A message loop that we can use as the file thread message loop.
	MessageLoop message_loop_;
	};

	// Test fallback behavior for a nonexistent file.
	TEST_F(JsonPrefStoreTest, NonExistentFile) {
	FilePath bogus_input_file = data_dir_.AppendASCII("read.txt");
	ASSERT_FALSE(file_util::PathExists(bogus_input_file));
	scoped_refptr<JsonPrefStore> pref_store =
	new JsonPrefStore(
	bogus_input_file, message_loop_.message_loop_proxy());
	EXPECT_EQ(PersistentPrefStore::PREF_READ_ERROR_NO_FILE,
	pref_store->ReadPrefs());
	EXPECT_FALSE(pref_store->ReadOnly());
	}

	// Test fallback behavior for an invalid file.
	TEST_F(JsonPrefStoreTest, InvalidFile) {
	FilePath invalid_file_original = data_dir_.AppendASCII("invalid.json");
	FilePath invalid_file = temp_dir_.path().AppendASCII("invalid.json");
	ASSERT_TRUE(file_util::CopyFile(invalid_file_original, invalid_file));
	scoped_refptr<JsonPrefStore> pref_store =
	new JsonPrefStore(
	invalid_file, message_loop_.message_loop_proxy());
	EXPECT_EQ(PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE,
	pref_store->ReadPrefs());
	EXPECT_FALSE(pref_store->ReadOnly());

	// The file should have been moved aside.
	EXPECT_FALSE(file_util::PathExists(invalid_file));
	FilePath moved_aside = temp_dir_.path().AppendASCII("invalid.bad");
	EXPECT_TRUE(file_util::PathExists(moved_aside));
	EXPECT_TRUE(file_util::TextContentsEqual(invalid_file_original,
	moved_aside));
	}

	// This function is used to avoid code duplication while testing synchronous and
	// asynchronous version of the JsonPrefStore loading.
	void RunBasicJsonPrefStoreTest(JsonPrefStore* pref_store,
	const FilePath& output_file,
	const FilePath& golden_output_file) {
	const char kNewWindowsInTabs[] = "tabs.new_windows_in_tabs";
	const char kMaxTabs[] = "tabs.max_tabs";
	const char kLongIntPref[] = "long_int.pref";

	std::string cnn("http://www.cnn.com");

	const Value* actual;
	EXPECT_TRUE(pref_store->GetValue(kHomePage, &actual));
	std::string string_value;
	EXPECT_TRUE(actual->GetAsString(&string_value));
	EXPECT_EQ(cnn, string_value);

	const char kSomeDirectory[] = "some_directory";

	EXPECT_TRUE(pref_store->GetValue(kSomeDirectory, &actual));
	FilePath::StringType path;
	EXPECT_TRUE(actual->GetAsString(&path));
	EXPECT_EQ(FilePath::StringType(FILE_PATH_LITERAL("/usr/local/")), path);
	FilePath some_path(FILE_PATH_LITERAL("/usr/sbin/"));

	pref_store->SetValue(kSomeDirectory, new StringValue(some_path.value()));
	EXPECT_TRUE(pref_store->GetValue(kSomeDirectory, &actual));
	EXPECT_TRUE(actual->GetAsString(&path));
	EXPECT_EQ(some_path.value(), path);

	// Test reading some other data types from sub-dictionaries.
	EXPECT_TRUE(pref_store->GetValue(kNewWindowsInTabs, &actual));
	bool boolean = false;
	EXPECT_TRUE(actual->GetAsBoolean(&boolean));
	EXPECT_TRUE(boolean);

	pref_store->SetValue(kNewWindowsInTabs, new FundamentalValue(false));
	EXPECT_TRUE(pref_store->GetValue(kNewWindowsInTabs, &actual));
	EXPECT_TRUE(actual->GetAsBoolean(&boolean));
	EXPECT_FALSE(boolean);

	EXPECT_TRUE(pref_store->GetValue(kMaxTabs, &actual));
	int integer = 0;
	EXPECT_TRUE(actual->GetAsInteger(&integer));
	EXPECT_EQ(20, integer);
	pref_store->SetValue(kMaxTabs, new FundamentalValue(10));
	EXPECT_TRUE(pref_store->GetValue(kMaxTabs, &actual));
	EXPECT_TRUE(actual->GetAsInteger(&integer));
	EXPECT_EQ(10, integer);

	pref_store->SetValue(kLongIntPref,
	new StringValue(base::Int64ToString(214748364842LL)));
	EXPECT_TRUE(pref_store->GetValue(kLongIntPref, &actual));
	EXPECT_TRUE(actual->GetAsString(&string_value));
	int64 value;
	base::StringToInt64(string_value, &value);
	EXPECT_EQ(214748364842LL, value);

	// Serialize and compare to expected output.
	ASSERT_TRUE(file_util::PathExists(golden_output_file));
	pref_store->CommitPendingWrite();
	MessageLoop::current()->RunUntilIdle();
	EXPECT_TRUE(file_util::TextContentsEqual(golden_output_file, output_file));
	ASSERT_TRUE(file_util::Delete(output_file, false));
	}

	TEST_F(JsonPrefStoreTest, Basic) {
	ASSERT_TRUE(file_util::CopyFile(data_dir_.AppendASCII("read.json"),
	temp_dir_.path().AppendASCII("write.json")));

	// Test that the persistent value can be loaded.
	FilePath input_file = temp_dir_.path().AppendASCII("write.json");
	ASSERT_TRUE(file_util::PathExists(input_file));
	scoped_refptr<JsonPrefStore> pref_store =
	new JsonPrefStore(
	input_file, message_loop_.message_loop_proxy());
	ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_NONE, pref_store->ReadPrefs());
	ASSERT_FALSE(pref_store->ReadOnly());

	// The JSON file looks like this:
	// {
	// "homepage": "http://www.cnn.com",
	// "some_directory": "/usr/local/",
	// "tabs": {
	// "new_windows_in_tabs": true,
	// "max_tabs": 20
	// }
	// }

	RunBasicJsonPrefStoreTest(pref_store,
	input_file,
	data_dir_.AppendASCII("write.golden.json"));
	}

	TEST_F(JsonPrefStoreTest, BasicAsync) {
	ASSERT_TRUE(file_util::CopyFile(data_dir_.AppendASCII("read.json"),
	temp_dir_.path().AppendASCII("write.json")));

	// Test that the persistent value can be loaded.
	FilePath input_file = temp_dir_.path().AppendASCII("write.json");
	ASSERT_TRUE(file_util::PathExists(input_file));
	scoped_refptr<JsonPrefStore> pref_store =
	new JsonPrefStore(
	input_file, message_loop_.message_loop_proxy());

	{
	MockPrefStoreObserver mock_observer;
	pref_store->AddObserver(&mock_observer);

	MockReadErrorDelegate* mock_error_delegate = new MockReadErrorDelegate;
	pref_store->ReadPrefsAsync(mock_error_delegate);

	EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(1);
	EXPECT_CALL(*mock_error_delegate,
	OnError(PersistentPrefStore::PREF_READ_ERROR_NONE)).Times(0);
	message_loop_.RunUntilIdle();
	pref_store->RemoveObserver(&mock_observer);

	ASSERT_FALSE(pref_store->ReadOnly());
	}

	// The JSON file looks like this:
	// {
	// "homepage": "http://www.cnn.com",
	// "some_directory": "/usr/local/",
	// "tabs": {
	// "new_windows_in_tabs": true,
	// "max_tabs": 20
	// }
	// }

	RunBasicJsonPrefStoreTest(pref_store,
	input_file,
	data_dir_.AppendASCII("write.golden.json"));
	}

	// Tests asynchronous reading of the file when there is no file.
	TEST_F(JsonPrefStoreTest, AsyncNonExistingFile) {
	FilePath bogus_input_file = data_dir_.AppendASCII("read.txt");
	ASSERT_FALSE(file_util::PathExists(bogus_input_file));
	scoped_refptr<JsonPrefStore> pref_store =
	new JsonPrefStore(
	bogus_input_file, message_loop_.message_loop_proxy());
	MockPrefStoreObserver mock_observer;
	pref_store->AddObserver(&mock_observer);

	MockReadErrorDelegate *mock_error_delegate = new MockReadErrorDelegate;
	pref_store->ReadPrefsAsync(mock_error_delegate);

	EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(1);
	EXPECT_CALL(*mock_error_delegate,
	OnError(PersistentPrefStore::PREF_READ_ERROR_NO_FILE)).Times(1);
	message_loop_.RunUntilIdle();
	pref_store->RemoveObserver(&mock_observer);

	EXPECT_FALSE(pref_store->ReadOnly());
	}

	TEST_F(JsonPrefStoreTest, NeedsEmptyValue) {
	FilePath pref_file = temp_dir_.path().AppendASCII("write.json");

	ASSERT_TRUE(file_util::CopyFile(
	data_dir_.AppendASCII("read.need_empty_value.json"),
	pref_file));

	// Test that the persistent value can be loaded.
	ASSERT_TRUE(file_util::PathExists(pref_file));
	scoped_refptr<JsonPrefStore> pref_store =
	new JsonPrefStore(
	pref_file, message_loop_.message_loop_proxy());
	ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_NONE, pref_store->ReadPrefs());
	ASSERT_FALSE(pref_store->ReadOnly());

	// The JSON file looks like this:
	// {
	// "list": [ 1 ],
	// "list_needs_empty_value": [ 2 ],
	// "dict": {
	// "dummy": true,
	// },
	// "dict_needs_empty_value": {
	// "dummy": true,
	// },
	// }

	// Set flag to preserve empty values for the following keys.
	pref_store->MarkNeedsEmptyValue("list_needs_empty_value");
	pref_store->MarkNeedsEmptyValue("dict_needs_empty_value");

	// Set all keys to empty values.
	pref_store->SetValue("list", new base::ListValue);
	pref_store->SetValue("list_needs_empty_value", new base::ListValue);
	pref_store->SetValue("dict", new base::DictionaryValue);
	pref_store->SetValue("dict_needs_empty_value", new base::DictionaryValue);

	// Write to file.
	pref_store->CommitPendingWrite();
	MessageLoop::current()->RunUntilIdle();

	// Compare to expected output.
	FilePath golden_output_file =
	data_dir_.AppendASCII("write.golden.need_empty_value.json");
	ASSERT_TRUE(file_util::PathExists(golden_output_file));
	EXPECT_TRUE(file_util::TextContentsEqual(golden_output_file, pref_file));
	}

	} // namespace base