Implement fetching, caching and retrieval of external policy data

chrome/browser/policy/cloud/cloud_external_data_manager_base_unittest.cc

Index: chrome/browser/policy/cloud/cloud_external_data_manager_base_unittest.cc
diff --git a/chrome/browser/policy/cloud/cloud_external_data_manager_base_unittest.cc b/chrome/browser/policy/cloud/cloud_external_data_manager_base_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b56a9889d35bdfac934bf775b242d7c046879728
--- /dev/null
+++ b/chrome/browser/policy/cloud/cloud_external_data_manager_base_unittest.cc
@@ -0,0 +1,753 @@
+// Copyright 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 "chrome/browser/policy/cloud/cloud_external_data_manager_base.h"
+
+#include <map>
+#include <string>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/files/scoped_temp_dir.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/run_loop.h"
+#include "base/sequenced_task_runner.h"
+#include "base/sha1.h"
+#include "base/stl_util.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/values.h"
+#include "chrome/browser/policy/cloud/cloud_external_data_store.h"
+#include "chrome/browser/policy/cloud/mock_cloud_policy_store.h"
+#include "chrome/browser/policy/cloud/resource_cache.h"
+#include "chrome/browser/policy/external_data_fetcher.h"
+#include "chrome/browser/policy/policy_map.h"
+#include "chrome/browser/policy/policy_types.h"
+#include "content/public/test/test_browser_thread_bundle.h"
+#include "net/url_request/test_url_fetcher_factory.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "net/url_request/url_fetcher_factory.h"
+#include "net/url_request/url_request_test_util.h"
+#include "policy/policy_constants.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "url/gurl.h"
+
+namespace policy {
+
+namespace {
+
+// A string policy.
+const char kStringPolicy[] = "StringPolicy";
+// A policy that may reference up to 10 bytes of external data.
+const char k10BytePolicy[] = "10BytePolicy";
+// A policy that may reference up to 20 bytes of external data.
+const char k20BytePolicy[] = "20BytePolicy";
+// A nonexistent policy.
+const char kUnknownPolicy[] = "UnknownPolicy";
+
+const char k10BytePolicyURL[] = "http://localhost/10_bytes";
+const char k20BytePolicyURL[] = "http://localhost/20_bytes";
+
+const char k10ByteData[] = "10 bytes..";
+const char k20ByteData[] = "20 bytes............";
+
+const PolicyDefinitionList::Entry kPolicyDefinitionListEntries[] = {
+  { kStringPolicy, base::Value::TYPE_STRING, false, 1, 0 },
+  { k10BytePolicy, base::Value::TYPE_DICTIONARY, false, 2, 10 },
+  { k20BytePolicy, base::Value::TYPE_DICTIONARY, false, 3, 20 },
+};
+
+const PolicyDefinitionList kPolicyDefinitionList = {
+  kPolicyDefinitionListEntries,
+  kPolicyDefinitionListEntries + arraysize(kPolicyDefinitionListEntries),
+};
+
+const char kCacheKey[] = "data";
+
+class FetchAttemptBlockingURLFetcherFactory : public net::URLFetcherFactory {
+ public:
+  FetchAttemptBlockingURLFetcherFactory();
+  virtual ~FetchAttemptBlockingURLFetcherFactory();
+
+  bool GetFetchAttempted() const;
+  void ClearFetchAttempted();

[Joao da Silva, 2013/07/19 11:15:15]

IIUC this class is meant to prevent creation of fetchers for unknown URLs, and
to check if that ever happened. If so then it would suffice to
ADD_FATAL_FAILURE() in CreateURLFetcher(), return NULL from there, and spin the
loop on TearDown to make sure no unexpected fetchers were started.

Also, these two are always used together in the tests, maybe combine into one?
(in case you don't take the suggestion above)

   bool GetFetchAttemptedAndClear()

[bartfab (slow), 2013/07/19 13:06:30]

Done.

+
+  // net::URLFetcherFactory:
+  virtual net::URLFetcher* CreateURLFetcher(
+      int id,
+      const GURL& url,
+      net::URLFetcher::RequestType request_type,
+      net::URLFetcherDelegate* delegate) OVERRIDE;
+
+ private:
+  bool fetch_attempted_;
+
+  DISALLOW_COPY_AND_ASSIGN(FetchAttemptBlockingURLFetcherFactory);
+};
+
+FetchAttemptBlockingURLFetcherFactory::FetchAttemptBlockingURLFetcherFactory()
+    : fetch_attempted_(false) {
+}
+
+FetchAttemptBlockingURLFetcherFactory::
+    ~FetchAttemptBlockingURLFetcherFactory() {
+}
+
+bool FetchAttemptBlockingURLFetcherFactory::GetFetchAttempted() const {
+  return fetch_attempted_;
+}
+
+void FetchAttemptBlockingURLFetcherFactory::ClearFetchAttempted() {
+  fetch_attempted_ = false;
+}
+
+net::URLFetcher* FetchAttemptBlockingURLFetcherFactory::CreateURLFetcher(
+    int id,
+    const GURL& url,
+    net::URLFetcher::RequestType request_type,
+    net::URLFetcherDelegate* delegate) {
+  fetch_attempted_ = true;
+  return NULL;
+}
+
+}  // namespace
+
+class CouldExternalDataManagerBaseTest : public testing::Test {
+ protected:
+  CouldExternalDataManagerBaseTest();
+
+  virtual void SetUp() OVERRIDE;
+  virtual void TearDown() OVERRIDE;
+
+  void SetUpExternalDataManager();
+
+  scoped_ptr<base::DictionaryValue> ConstructMetadata(const std::string& url,
+                                                      const std::string& hash);
+  void SetExternalDataReference(const std::string& policy,
+                                scoped_ptr<base::DictionaryValue> metadata);
+
+  ExternalDataFetcher::FetchCallback ConstructFetchCallback(int id);
+  void ResetCallbackData();
+
+  void OnFetchDone(int id, scoped_ptr<std::string> data);
+
+  void FetchAll();
+
+  content::TestBrowserThreadBundle thread_bundle_;
+
+  base::ScopedTempDir temp_dir_;
+  scoped_ptr<ResourceCache> resource_cache_;
+  MockCloudPolicyStore cloud_policy_store_;
+  scoped_refptr<net::TestURLRequestContextGetter> request_content_getter_;
+  FetchAttemptBlockingURLFetcherFactory default_fetcher_factory_;
+  net::FakeURLFetcherFactory fake_fetcher_factory_;
+
+  scoped_ptr<CloudExternalDataManagerBase> external_data_manager_;
+
+  std::map<int, std::string*> callback_data_;
+
+  DISALLOW_COPY_AND_ASSIGN(CouldExternalDataManagerBaseTest);
+};
+
+CouldExternalDataManagerBaseTest::CouldExternalDataManagerBaseTest()
+    : thread_bundle_(content::TestBrowserThreadBundle::IO_MAINLOOP),
+      fake_fetcher_factory_(&default_fetcher_factory_) {
+}
+
+void CouldExternalDataManagerBaseTest::SetUp() {
+  ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
+  resource_cache_.reset(new ResourceCache(temp_dir_.path()));
+  SetUpExternalDataManager();
+
+  // Set |kStringPolicy| to a string value.
+  cloud_policy_store_.policy_map_.Set(kStringPolicy,
+                                      POLICY_LEVEL_MANDATORY,
+                                      POLICY_SCOPE_USER,
+                                      new base::StringValue(std::string()),
+                                      NULL);
+  // Make |k10BytePolicy| reference 10 bytes of external data.
+  SetExternalDataReference(
+      k10BytePolicy,
+      ConstructMetadata(k10BytePolicyURL, base::SHA1HashString(k10ByteData)));
+  // Make |k20BytePolicy| reference 20 bytes of external data.
+  SetExternalDataReference(
+      k20BytePolicy,
+      ConstructMetadata(k20BytePolicyURL, base::SHA1HashString(k20ByteData)));
+  cloud_policy_store_.NotifyStoreLoaded();
+
+  request_content_getter_ = new net::TestURLRequestContextGetter(
+      base::MessageLoopProxy::current());
+}
+
+void CouldExternalDataManagerBaseTest::TearDown() {
+  ResetCallbackData();
+}
+
+void CouldExternalDataManagerBaseTest::SetUpExternalDataManager() {
+  external_data_manager_.reset(new CloudExternalDataManagerBase(
+      &kPolicyDefinitionList, base::MessageLoopProxy::current()));
+  external_data_manager_->SetExternalDataStore(make_scoped_ptr(
+      new CloudExternalDataStore(kCacheKey, resource_cache_.get())));
+  external_data_manager_->SetPolicyStore(&cloud_policy_store_);
+}
+
+scoped_ptr<base::DictionaryValue>
+    CouldExternalDataManagerBaseTest::ConstructMetadata(
+        const std::string& url,
+        const std::string& hash) {
+  scoped_ptr<base::DictionaryValue> metadata(new base::DictionaryValue);
+  metadata->SetStringWithoutPathExpansion("url", url);
+  metadata->SetStringWithoutPathExpansion("hash", base::HexEncode(hash.c_str(),
+                                                                  hash.size()));
+  return metadata.Pass();
+}
+
+void CouldExternalDataManagerBaseTest::SetExternalDataReference(
+    const std::string& policy,
+    scoped_ptr<base::DictionaryValue> metadata) {
+  cloud_policy_store_.policy_map_.Set(
+      policy,
+      POLICY_LEVEL_MANDATORY,
+      POLICY_SCOPE_USER,
+      metadata.release(),
+      new ExternalDataFetcher(
+          external_data_manager_->weak_factory_.GetWeakPtr(), policy));
+}
+
+ExternalDataFetcher::FetchCallback
+CouldExternalDataManagerBaseTest::ConstructFetchCallback(int id) {
+  return base::Bind(&CouldExternalDataManagerBaseTest::OnFetchDone,
+                    base::Unretained(this),
+                    id);
+}
+
+void CouldExternalDataManagerBaseTest::ResetCallbackData() {
+  STLDeleteValues(&callback_data_);
+}
+
+void CouldExternalDataManagerBaseTest::OnFetchDone(
+    int id,
+    scoped_ptr<std::string> data) {
+  delete callback_data_[id];
+  callback_data_[id] = data.release();
+}
+
+void CouldExternalDataManagerBaseTest::FetchAll() {
+  external_data_manager_->FetchAll();
+}
+
+// Verifies that when no valid external data reference has been set for a
+// policy, the attempt to retrieve the external data fails immediately.
+TEST_F(CouldExternalDataManagerBaseTest, FailToFetchInvalid) {
+  external_data_manager_->Connect(request_content_getter_);
+
+  // Attempt to retrieve external data for |kStringPolicy|, which is a string
+  // policy that does not reference any external data.
+  external_data_manager_->Fetch(kStringPolicy, ConstructFetchCallback(0));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  EXPECT_TRUE(callback_data_.find(0) != callback_data_.end());
+  EXPECT_FALSE(callback_data_[0]);
+  ResetCallbackData();
+
+  // Attempt to retrieve external data for |kUnknownPolicy|, which is not a
+  // known policy.
+  external_data_manager_->Fetch(kUnknownPolicy, ConstructFetchCallback(1));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  EXPECT_TRUE(callback_data_.find(1) != callback_data_.end());
+  EXPECT_FALSE(callback_data_[1]);
+  ResetCallbackData();
+
+  // Set an invalid external data reference for |k10BytePolicy|.
+  SetExternalDataReference(k10BytePolicy,
+                           ConstructMetadata(std::string(), std::string()));
+  cloud_policy_store_.NotifyStoreLoaded();
+
+  // Attempt to retrieve external data for |k10BytePolicy|, which now has an
+  // invalid reference.
+  external_data_manager_->Fetch(k10BytePolicy, ConstructFetchCallback(2));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  EXPECT_TRUE(callback_data_.find(2) != callback_data_.end());
+  EXPECT_FALSE(callback_data_[2]);
+  ResetCallbackData();
+}
+
+// Verifies that external data referenced by a policy is downloaded and cached
+// when first requested. Subsequent requests are served from the cache without
+// further download attempts.
+TEST_F(CouldExternalDataManagerBaseTest, DownloadAndCache) {
+  // Serve valid external data for |k10BytePolicy|.
+  fake_fetcher_factory_.SetFakeResponse(k10BytePolicyURL, k10ByteData, true);
+  external_data_manager_->Connect(request_content_getter_);
+
+  // Retrieve external data for |k10BytePolicy|. Verify that a download happens
+  // and the callback is invoked with the downloaded data.
+  external_data_manager_->Fetch(k10BytePolicy, ConstructFetchCallback(0));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  ASSERT_TRUE(callback_data_[0]);
+  EXPECT_EQ(k10ByteData, *callback_data_[0]);
+  ResetCallbackData();
+
+  // Stop serving external data for |k10BytePolicy|.
+  fake_fetcher_factory_.ClearFakeResponses();
+
+  // Retrieve external data for |k10BytePolicy| again. Verify that no download
+  // is attempted but the callback is still invoked with the expected data,
+  // served from the cache.
+  external_data_manager_->Fetch(k10BytePolicy, ConstructFetchCallback(1));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  ASSERT_TRUE(callback_data_[1]);
+  EXPECT_EQ(k10ByteData, *callback_data_[1]);
+  ResetCallbackData();
+
+  // Explicitly tell the external_data_manager_ to not make any download
+  // attempts.
+  external_data_manager_->Disconnect();
+
+  // Retrieve external data for |k10BytePolicy| again. Verify that even though
+  // downloads are not allowed, the callback is still invoked with the expected
+  // data, served from the cache.
+  external_data_manager_->Fetch(k10BytePolicy, ConstructFetchCallback(2));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  ASSERT_TRUE(callback_data_[2]);
+  EXPECT_EQ(k10ByteData, *callback_data_[2]);
+  ResetCallbackData();
+
+  // Verify that the downloaded data is present in the cache.
+  external_data_manager_.reset();
+  base::RunLoop().RunUntilIdle();
+  std::string data;
+  EXPECT_TRUE(CloudExternalDataStore(kCacheKey, resource_cache_.get()).Load(
+      k10BytePolicy, base::SHA1HashString(k10ByteData), 10, &data));
+  EXPECT_EQ(k10ByteData, data);
+}
+
+// Verifies that a request to download and cache all external data referenced by
+// policies is carried out correctly. Subsequent requests for the data are
+// served from the cache without further download attempts.
+TEST_F(CouldExternalDataManagerBaseTest, DownloadAndCacheAll) {
+  // Serve valid external data for |k10BytePolicy| and |k20BytePolicy|.
+  fake_fetcher_factory_.SetFakeResponse(k10BytePolicyURL, k10ByteData, true);
+  fake_fetcher_factory_.SetFakeResponse(k20BytePolicyURL, k20ByteData, true);
+  external_data_manager_->Connect(request_content_getter_);
+
+  // Request that external data referenced by all policies be downloaded.
+  FetchAll();
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+
+  // Stop serving external data for |k10BytePolicy| and |k20BytePolicy|.
+  fake_fetcher_factory_.ClearFakeResponses();
+
+  // Retrieve external data for |k10BytePolicy| and |k20BytePolicy|. Verify that
+  // no downloads are attempted but the callbacks are still invoked with the
+  // expected data, served from the cache.
+  external_data_manager_->Fetch(k10BytePolicy, ConstructFetchCallback(0));
+  external_data_manager_->Fetch(k20BytePolicy, ConstructFetchCallback(1));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(2u, callback_data_.size());
+  ASSERT_TRUE(callback_data_[0]);
+  EXPECT_EQ(k10ByteData, *callback_data_[0]);
+  ASSERT_TRUE(callback_data_[1]);
+  EXPECT_EQ(k20ByteData, *callback_data_[1]);
+  ResetCallbackData();
+
+  // Explicitly tell the external_data_manager_ to not make any download
+  // attempts.
+  external_data_manager_->Disconnect();
+
+  // Retrieve external data for |k10BytePolicy| and |k20BytePolicy|. Verify that
+  // even though downloads are not allowed, the callbacks are still invoked with
+  // the expected data, served from the cache.
+  external_data_manager_->Fetch(k10BytePolicy, ConstructFetchCallback(2));
+  external_data_manager_->Fetch(k20BytePolicy, ConstructFetchCallback(3));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(2u, callback_data_.size());
+  ASSERT_TRUE(callback_data_[2]);
+  EXPECT_EQ(k10ByteData, *callback_data_[2]);
+  ASSERT_TRUE(callback_data_[3]);
+  EXPECT_EQ(k20ByteData, *callback_data_[3]);
+  ResetCallbackData();
+
+  // Verify that the downloaded data is present in the cache.
+  external_data_manager_.reset();
+  base::RunLoop().RunUntilIdle();
+  CloudExternalDataStore cache(kCacheKey, resource_cache_.get());
+  std::string data;
+  EXPECT_TRUE(cache.Load(k10BytePolicy, base::SHA1HashString(k10ByteData), 10,
+                         &data));
+  EXPECT_EQ(k10ByteData, data);
+  EXPECT_TRUE(cache.Load(k20BytePolicy, base::SHA1HashString(k20ByteData), 20,
+                         &data));
+  EXPECT_EQ(k20ByteData, data);
+}
+
+// Verifies that when the external data referenced by a policy is not present in
+// the cache and downloads are not allowed, a request to retrieve the data is
+// enqueued and carried out when downloads become possible.
+TEST_F(CouldExternalDataManagerBaseTest, DownloadAfterConnect) {
+  // Attempt to retrieve external data for |k10BytePolicy|. Verify that the
+  // callback is not invoked as the request remains pending.
+  external_data_manager_->Fetch(k10BytePolicy, ConstructFetchCallback(0));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_TRUE(callback_data_.empty());
+  ResetCallbackData();
+
+  // Serve valid external data for |k10BytePolicy| and allow the
+  // external_data_manager_ to perform downloads.
+  fake_fetcher_factory_.SetFakeResponse(k10BytePolicyURL, k10ByteData, true);
+  external_data_manager_->Connect(request_content_getter_);
+
+  // Verify that a download happens and the callback is invoked with the
+  // downloaded data.
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  ASSERT_TRUE(callback_data_[0]);
+  EXPECT_EQ(k10ByteData, *callback_data_[0]);
+  ResetCallbackData();
+}
+
+// Verifies that when the external data referenced by a policy is not present in
+// the cache and cannot be downloaded at this time, a request to retrieve the
+// data is enqueued to be retried later.
+TEST_F(CouldExternalDataManagerBaseTest, DownloadError) {
+  // Make attempts to download the external data for |k20BytePolicy| fail with
+  // an error.
+  fake_fetcher_factory_.SetFakeResponse(k20BytePolicyURL, std::string(), false);
+  external_data_manager_->Connect(request_content_getter_);
+
+  // Attempt to retrieve external data for |k20BytePolicy|. Verify that the
+  // callback is not invoked as the download attempt fails and the request
+  // remains pending.
+  external_data_manager_->Fetch(k20BytePolicy, ConstructFetchCallback(0));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_TRUE(callback_data_.empty());
+  ResetCallbackData();
+
+  // Modify the external data reference for |k20BytePolicy|, allowing the
+  // download to be retried immediately.
+  SetExternalDataReference(
+      k20BytePolicy,
+      ConstructMetadata(k20BytePolicyURL, base::SHA1HashString(k10ByteData)));
+  cloud_policy_store_.NotifyStoreLoaded();
+
+  // Attempt to retrieve external data for |k20BytePolicy| again. Verify that
+  // no callback is invoked still as the download attempt fails again and the
+  // request remains pending.
+  external_data_manager_->Fetch(k20BytePolicy, ConstructFetchCallback(1));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_TRUE(callback_data_.empty());
+  ResetCallbackData();
+
+  // Modify the external data reference for |k20BytePolicy|, allowing the
+  // download to be retried immediately.
+  SetExternalDataReference(
+      k20BytePolicy,
+      ConstructMetadata(k20BytePolicyURL, base::SHA1HashString(k20ByteData)));
+  cloud_policy_store_.NotifyStoreLoaded();
+
+  // Serve external data for |k20BytePolicy| that does not match the hash
+  // specified in its current external data reference.
+  fake_fetcher_factory_.SetFakeResponse(k20BytePolicyURL, k10ByteData, true);
+
+  // Attempt to retrieve external data for |k20BytePolicy| again. Verify that
+  // no callback is invoked still as the downloaded succeeds but returns data
+  // that does not match the external data reference.
+  external_data_manager_->Fetch(k20BytePolicy, ConstructFetchCallback(2));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_TRUE(callback_data_.empty());
+  ResetCallbackData();
+
+  // Modify the external data reference for |k20BytePolicy|, allowing the
+  // download to be retried immediately. The external data reference now matches
+  // the data being served.
+  SetExternalDataReference(
+      k20BytePolicy,
+      ConstructMetadata(k20BytePolicyURL, base::SHA1HashString(k10ByteData)));
+  cloud_policy_store_.NotifyStoreLoaded();
+
+  // Attempt to retrieve external data for |k20BytePolicy| again. Verify that
+  // the current callback and the three previously enqueued callbacks are
+  // invoked with the downloaded data now.
+  external_data_manager_->Fetch(k20BytePolicy, ConstructFetchCallback(3));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(4u, callback_data_.size());
+  ASSERT_TRUE(callback_data_[0]);
+  EXPECT_EQ(k10ByteData, *callback_data_[0]);
+  ASSERT_TRUE(callback_data_[1]);
+  EXPECT_EQ(k10ByteData, *callback_data_[1]);
+  ASSERT_TRUE(callback_data_[2]);
+  EXPECT_EQ(k10ByteData, *callback_data_[2]);
+  ASSERT_TRUE(callback_data_[3]);
+  EXPECT_EQ(k10ByteData, *callback_data_[3]);
+  ResetCallbackData();
+}
+
+// Verifies that when the external data referenced by a policy is present in the
+// cache, a request to retrieve it is served from the cache without any download
+// attempts.
+TEST_F(CouldExternalDataManagerBaseTest, LoadFromCache) {
+  // Store valid external data for |k10BytePolicy| in the cache.
+  external_data_manager_.reset();
+  base::RunLoop().RunUntilIdle();
+  EXPECT_TRUE(CloudExternalDataStore(kCacheKey, resource_cache_.get()).Store(
+      k10BytePolicy, base::SHA1HashString(k10ByteData), k10ByteData));
+
+  // Instantiate an external_data_manager_ that uses the primed cache.
+  SetUpExternalDataManager();
+  external_data_manager_->Connect(request_content_getter_);
+
+  // Retrieve external data for |k10BytePolicy|. Verify that no download is
+  // attempted but the callback is still invoked with the expected data, served
+  // from the cache.
+  external_data_manager_->Fetch(k10BytePolicy, ConstructFetchCallback(0));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  ASSERT_TRUE(callback_data_[0]);
+  EXPECT_EQ(k10ByteData, *callback_data_[0]);
+  ResetCallbackData();
+}
+
+// Verifies that cache entries which do not correspond to the external data
+// referenced by any policy are pruned on startup.
+TEST_F(CouldExternalDataManagerBaseTest, PruneCacheOnStartup) {
+  external_data_manager_.reset();
+  base::RunLoop().RunUntilIdle();
+  scoped_ptr<CloudExternalDataStore>
+      cache(new CloudExternalDataStore(kCacheKey, resource_cache_.get()));
+  // Store valid external data for |k10BytePolicy| in the cache.
+  EXPECT_TRUE(cache->Store(k10BytePolicy,
+                           base::SHA1HashString(k10ByteData),
+                           k10ByteData));
+  // Store external data for |k20BytePolicy| that does not match the hash in its
+  // external data reference.
+  EXPECT_TRUE(cache->Store(k20BytePolicy,
+                           base::SHA1HashString(k10ByteData),
+                           k10ByteData));
+  // Store external data for |kUnknownPolicy|, which is not a known policy and
+  // therefore, cannot be referencing any external data.
+  EXPECT_TRUE(cache->Store(kUnknownPolicy,
+                           base::SHA1HashString(k10ByteData),
+                           k10ByteData));
+  cache.reset();
+
+  // Instantiate and destroy an ExternalDataManager that uses the primed cache.
+  SetUpExternalDataManager();
+  external_data_manager_.reset();
+  base::RunLoop().RunUntilIdle();
+
+  cache.reset(new CloudExternalDataStore(kCacheKey, resource_cache_.get()));
+  std::string data;
+  // Verify that the valid external data for |k10BytePolicy| is still in the
+  // cache.
+  EXPECT_TRUE(cache->Load(k10BytePolicy, base::SHA1HashString(k10ByteData),
+                          10, &data));
+  EXPECT_EQ(k10ByteData, data);
+  // Verify that the external data for |k20BytePolicy| and |kUnknownPolicy| has
+  // been pruned from the cache.
+  EXPECT_FALSE(cache->Load(k20BytePolicy, base::SHA1HashString(k10ByteData),
+                           20, &data));
+  EXPECT_FALSE(cache->Load(kUnknownPolicy, base::SHA1HashString(k10ByteData),
+                           20, &data));
+}
+
+// Verifies that when the external data referenced by a policy is present in the
+// cache and the reference changes, the old data is pruned from the cache.
+TEST_F(CouldExternalDataManagerBaseTest, PruneCacheOnChange) {
+  // Store valid external data for |k20BytePolicy| in the cache.
+  external_data_manager_.reset();
+  base::RunLoop().RunUntilIdle();
+  scoped_ptr<CloudExternalDataStore>
+      cache(new CloudExternalDataStore(kCacheKey, resource_cache_.get()));
+  EXPECT_TRUE(cache->Store(k20BytePolicy,
+                           base::SHA1HashString(k20ByteData),
+                           k20ByteData));
+  cache.reset();
+
+  // Instantiate an ExternalDataManager that uses the primed cache.
+  SetUpExternalDataManager();
+  external_data_manager_->Connect(request_content_getter_);
+
+  // Modify the external data reference for |k20BytePolicy|.
+  SetExternalDataReference(
+      k20BytePolicy,
+      ConstructMetadata(k20BytePolicyURL, base::SHA1HashString(k10ByteData)));
+  cloud_policy_store_.NotifyStoreLoaded();
+
+  // Verify that the old external data for |k20BytePolicy| has been pruned from
+  // the cache.
+  external_data_manager_.reset();
+  base::RunLoop().RunUntilIdle();
+  cache.reset(new CloudExternalDataStore(kCacheKey, resource_cache_.get()));
+  std::string data;
+  EXPECT_FALSE(cache->Load(k20BytePolicy, base::SHA1HashString(k20ByteData), 20,
+                           &data));
+}
+
+// Verifies that corrupt cache entries are detected and deleted when accessed.
+TEST_F(CouldExternalDataManagerBaseTest, CacheCorruption) {
+  external_data_manager_.reset();
+  base::RunLoop().RunUntilIdle();
+  scoped_ptr<CloudExternalDataStore>
+      cache(new CloudExternalDataStore(kCacheKey, resource_cache_.get()));
+  // Store external data for |k10BytePolicy| that exceeds the maximal external
+  // data size allowed for that policy.
+  EXPECT_TRUE(cache->Store(k10BytePolicy,
+                           base::SHA1HashString(k20ByteData),
+                           k20ByteData));
+  // Store external data for |k20BytePolicy| that is corrupted and does not
+  // match the expected hash.
+  EXPECT_TRUE(cache->Store(k20BytePolicy,
+                           base::SHA1HashString(k20ByteData),
+                           k10ByteData));
+  cache.reset();
+
+  SetUpExternalDataManager();
+  // Serve external data for |k10BytePolicy| that exceeds the maximal external
+  // data size allowed for that policy.
+  fake_fetcher_factory_.SetFakeResponse(k10BytePolicyURL, k20ByteData, true);
+  external_data_manager_->Connect(request_content_getter_);
+
+  // Modify the external data reference for |k10BytePolicy| to match the
+  // external data being served.
+  SetExternalDataReference(
+      k10BytePolicy,
+      ConstructMetadata(k10BytePolicyURL, base::SHA1HashString(k20ByteData)));
+  cloud_policy_store_.NotifyStoreLoaded();
+
+  // Retrieve external data for |k10BytePolicy|. Verify that the callback is
+  // not invoked as the cached and downloaded external data exceed the maximal
+  // size allowed for this policy and the request remains pending.
+  external_data_manager_->Fetch(k10BytePolicy, ConstructFetchCallback(0));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_TRUE(callback_data_.empty());
+  ResetCallbackData();
+
+  // Serve valid external data for |k20BytePolicy|.
+  fake_fetcher_factory_.SetFakeResponse(k20BytePolicyURL, k20ByteData, true);
+
+  // Retrieve external data for |k20BytePolicy|. Verify that the callback is
+  // invoked with the valid downloaded data, not the invalid data in the cache.
+  external_data_manager_->Fetch(k20BytePolicy, ConstructFetchCallback(1));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  ASSERT_TRUE(callback_data_[1]);
+  EXPECT_EQ(k20ByteData, *callback_data_[1]);
+  ResetCallbackData();
+
+  external_data_manager_.reset();
+  base::RunLoop().RunUntilIdle();
+  cache.reset(new CloudExternalDataStore(kCacheKey, resource_cache_.get()));
+  std::string data;
+  // Verify that the invalid external data for |k10BytePolicy| has been pruned
+  // from the cache. Load() will return |false| in two cases:
+  // 1) The cache entry for |k10BytePolicy| has been pruned.
+  // 2) The cache entry for |k10BytePolicy| still exists but the cached data
+  //    does not match the expected hash or exceeds the maximum size allowed.
+  // To test for the former, Load() is called with a maximum data size and hash
+  // that would allow the data originally written to the cache to be loaded.
+  // When this fails, it is certain that the original data is no longer present
+  // in the cache.
+  EXPECT_FALSE(cache->Load(k10BytePolicy, base::SHA1HashString(k20ByteData), 20,
+                           &data));
+  // Verify that the invalid external data for |k20BytePolicy| has been replaced
+  // with the downloaded valid data in the cache.
+  EXPECT_TRUE(cache->Load(k20BytePolicy, base::SHA1HashString(k20ByteData), 20,
+                          &data));
+  EXPECT_EQ(k20ByteData, data);
+}
+
+// Verifies that when the external data reference for a policy changes while a
+// download of the external data for that policy is pending, the download is
+// immediately retried using the new reference.
+TEST_F(CouldExternalDataManagerBaseTest, PolicyChangeWhileDownloadPending) {
+  // Make attempts to download the external data for |k10BytePolicy| and
+  // |k20BytePolicy| fail with an error.
+  fake_fetcher_factory_.SetFakeResponse(k10BytePolicyURL, std::string(), false);
+  fake_fetcher_factory_.SetFakeResponse(k20BytePolicyURL, std::string(), false);
+  external_data_manager_->Connect(request_content_getter_);
+
+  // Attempt to retrieve external data for |k10BytePolicy| and |k20BytePolicy|.
+  // Verify that no callbacks are invoked as the download attempts fail and the
+  // requests remain pending.
+  external_data_manager_->Fetch(k10BytePolicy, ConstructFetchCallback(0));
+  external_data_manager_->Fetch(k20BytePolicy, ConstructFetchCallback(1));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_TRUE(callback_data_.empty());
+  ResetCallbackData();
+
+  // Modify the external data reference for |k10BytePolicy| to be invalid.
+  // Verify that the callback is invoked as the policy no longer has a valid
+  // external data reference.
+  cloud_policy_store_.policy_map_.Erase(k10BytePolicy);
+  cloud_policy_store_.NotifyStoreLoaded();
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  EXPECT_TRUE(callback_data_.find(0) != callback_data_.end());
+  EXPECT_FALSE(callback_data_[0]);
+  ResetCallbackData();
+
+  // Serve valid external data for |k20BytePolicy|.
+  fake_fetcher_factory_.ClearFakeResponses();
+  fake_fetcher_factory_.SetFakeResponse(k20BytePolicyURL, k10ByteData, true);
+
+  // Modify the external data reference for |k20BytePolicy| to match the
+  // external data now being served. Verify that the callback is invoked with
+  // the downloaded data.
+  SetExternalDataReference(
+      k20BytePolicy,
+      ConstructMetadata(k20BytePolicyURL, base::SHA1HashString(k10ByteData)));
+  cloud_policy_store_.NotifyStoreLoaded();
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(default_fetcher_factory_.GetFetchAttempted());
+  default_fetcher_factory_.ClearFetchAttempted();
+  EXPECT_EQ(1u, callback_data_.size());
+  ASSERT_TRUE(callback_data_[1]);
+  EXPECT_EQ(k10ByteData, *callback_data_[1]);
+  ResetCallbackData();
+}
+
+}  // namespace policy