Provide monitoring of usage for a storage type and origin

webkit/browser/quota/storage_monitor_unittest.cc

Index: webkit/browser/quota/storage_monitor_unittest.cc
diff --git a/webkit/browser/quota/storage_monitor_unittest.cc b/webkit/browser/quota/storage_monitor_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e2768f08433875fb99fba900b9bf89facefadbba
--- /dev/null
+++ b/webkit/browser/quota/storage_monitor_unittest.cc
@@ -0,0 +1,584 @@
+// 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 <vector>
+
+#include "base/files/scoped_temp_dir.h"
+#include "base/message_loop/message_loop.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/run_loop.h"
+#include "net/base/net_util.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "webkit/browser/quota/mock_special_storage_policy.h"
+#include "webkit/browser/quota/mock_storage_client.h"
+#include "webkit/browser/quota/quota_manager.h"
+#include "webkit/browser/quota/quota_manager_proxy.h"
+#include "webkit/browser/quota/storage_monitor.h"
+#include "webkit/browser/quota/storage_observer.h"
+
+namespace quota {
+
+namespace {
+
+const char kDefaultOrigin[] = "http://www.foo.com/";
+const char kAlternativeOrigin[] = "http://www.bar.com/";
+
+class MockObserver : public StorageObserver {
+ public:
+  const StorageObserver::Event& LastEvent() const {
+    CHECK(!events_.empty());
+    return events_.back();
+  }
+
+  int EventCount() const {
+    return events_.size();
+  }
+
+  // StorageObserver implementation:
+  virtual void OnStorageEvent(const StorageObserver::Event& event) OVERRIDE {
+    events_.push_back(event);
+  }
+
+ private:
+  std::vector<StorageObserver::Event> events_;
+};
+
+// A mock quota manager for overriding GetUsageAndQuotaForWebApps().
+class UsageMockQuotaManager : public QuotaManager {
+ public:
+  UsageMockQuotaManager(SpecialStoragePolicy* special_storage_policy)
+      : QuotaManager(
+            false,
+            base::FilePath(),
+            base::MessageLoopProxy::current().get(),
+            base::MessageLoopProxy::current().get(),
+            special_storage_policy),
+        callback_usage_(0),
+        callback_quota_(0),
+        callback_status_(kQuotaStatusOk) {
+  }
+
+  void SetCallbackParams(int64 usage, int64 quota, QuotaStatusCode status) {
+    callback_quota_ = quota;
+    callback_usage_ = usage;
+    callback_status_ = status;
+  }
+
+  virtual void GetUsageAndQuotaForWebApps(
+      const GURL& origin,
+      StorageType type,
+      const GetUsageAndQuotaCallback& callback) OVERRIDE {
+    callback.Run(callback_status_, callback_usage_, callback_quota_);
+  }
+
+ protected:
+  virtual ~UsageMockQuotaManager() {}
+
+ private:
+  int64 callback_usage_;
+  int64 callback_quota_;
+  QuotaStatusCode callback_status_;
+};
+
+}  // namespace
+
+class StorageObserverListTest : public testing::Test {
+ protected:
+  void DispatchPendingEvents(StorageObserverList& observer_list) {
+    observer_list.DispatchPendingEvent();
+  }
+
+  void SetLastNotificationTime(StorageObserverList& observer_list,
+                               StorageObserver* observer) {
+    ASSERT_TRUE(observer_list.observers_.find(observer) !=
+                observer_list.observers_.end());
+
+    StorageObserverList::ObserverState& state =
+        observer_list.observers_[observer];
+    state.last_notification_time = base::Time::Now() - state.rate;
+  }
+};
+
+class StorageTestBase : public StorageObserverListTest {
+ public:
+  virtual void SetUp() OVERRIDE {
+    storage_policy_ = new MockSpecialStoragePolicy();
+    quota_manager_ = new UsageMockQuotaManager(storage_policy_.get());
+  }
+
+  virtual void TearDown() OVERRIDE {
+    // This ensures the quota manager is destroyed correctly.
+    quota_manager_ = NULL;
+    base::RunLoop().RunUntilIdle();
+  }
+
+ protected:
+  base::MessageLoop message_loop_;
+  scoped_refptr<MockSpecialStoragePolicy> storage_policy_;
+  scoped_refptr<UsageMockQuotaManager> quota_manager_;
+};
+
+// Tests for StorageObserverList:
+
+// Test dispatching events to one observer.
+TEST_F(StorageObserverListTest, DispatchEventToSingleObserver) {
+  // A message loop is required as StorageObserverList may schedule jobs.
+  base::MessageLoop loop(base::MessageLoop::TYPE_DEFAULT);
+
+  StorageObserver::MonitorParams params(kStorageTypePersistent,
+                                        GURL(kDefaultOrigin),
+                                        2000, false);
+  MockObserver mock_observer;
+  StorageObserverList observer_list;
+  observer_list.AddObserver(&mock_observer, params);
+
+  StorageObserver::Event event;
+  event.filter = params.filter;
+
+  // Verify that the first event is dispatched immediately.
+  event.quota = 1;
+  event.usage = 1;
+  observer_list.OnStorageChange(event);
+  EXPECT_EQ(event, mock_observer.LastEvent());
+  EXPECT_EQ(1, mock_observer.EventCount());
+  EXPECT_EQ(NULL, observer_list.GetPendingEvent());
+  EXPECT_EQ(0, observer_list.GetRequiredUpdatesCount());
+
+  // Verify that the next event is pending.
+  event.quota = 2;
+  event.usage = 2;
+  observer_list.OnStorageChange(event);
+  EXPECT_EQ(1, mock_observer.EventCount());
+  ASSERT_TRUE(observer_list.GetPendingEvent());
+  EXPECT_EQ(event, *observer_list.GetPendingEvent());
+  EXPECT_EQ(1, observer_list.GetRequiredUpdatesCount());
+
+  // Fake the last notification time so that an event will be dispatched.
+  SetLastNotificationTime(observer_list, &mock_observer);
+  event.quota = 3;
+  event.usage = 3;
+  observer_list.OnStorageChange(event);
+  EXPECT_EQ(event, mock_observer.LastEvent());
+  EXPECT_EQ(2, mock_observer.EventCount());
+  EXPECT_EQ(NULL, observer_list.GetPendingEvent());
+  EXPECT_EQ(0, observer_list.GetRequiredUpdatesCount());
+
+  // Remove the observer.
+  event.quota = 4;
+  event.usage = 4;
+  observer_list.RemoveObserver(&mock_observer);
+  observer_list.OnStorageChange(event);
+  EXPECT_EQ(2, mock_observer.EventCount());
+  EXPECT_EQ(NULL, observer_list.GetPendingEvent());
+}
+
+// Test dispatching events to multiple observers.
+TEST_F(StorageObserverListTest, DispatchEventToMultipleObservers) {
+  // A message loop is required as StorageObserverList may schedule jobs.
+  base::MessageLoop loop(base::MessageLoop::TYPE_DEFAULT);
+
+  MockObserver mock_observer1;
+  MockObserver mock_observer2;
+  StorageObserverList observer_list;
+  StorageObserver::Filter filter(kStorageTypePersistent,
+                                 GURL(kDefaultOrigin));
+  observer_list.AddObserver(
+      &mock_observer1, StorageObserver::MonitorParams(filter, 2000, false));
+  observer_list.AddObserver(
+      &mock_observer2, StorageObserver::MonitorParams(filter, 4000, false));
+
+  StorageObserver::Event event;
+  event.filter = filter;
+
+  // Verify that the first event is dispatched immediately.
+  event.quota = 1;
+  event.usage = 1;
+  observer_list.OnStorageChange(event);
+  EXPECT_EQ(event, mock_observer1.LastEvent());
+  EXPECT_EQ(event, mock_observer2.LastEvent());
+  EXPECT_EQ(1, mock_observer1.EventCount());
+  EXPECT_EQ(1, mock_observer2.EventCount());
+  EXPECT_EQ(NULL, observer_list.GetPendingEvent());
+  EXPECT_EQ(0, observer_list.GetRequiredUpdatesCount());
+
+  // Fake the last notification time so that observer1 will receive the next
+  // event, but it will be pending for observer2.
+  SetLastNotificationTime(observer_list, &mock_observer1);
+  event.quota = 2;
+  event.usage = 2;
+  observer_list.OnStorageChange(event);
+  EXPECT_EQ(event, mock_observer1.LastEvent());
+  EXPECT_EQ(2, mock_observer1.EventCount());
+  EXPECT_EQ(1, mock_observer2.EventCount());
+  ASSERT_TRUE(observer_list.GetPendingEvent());
+  EXPECT_EQ(event, *observer_list.GetPendingEvent());
+  EXPECT_EQ(1, observer_list.GetRequiredUpdatesCount());
+
+  // Now dispatch the pending event to observer2.
+  SetLastNotificationTime(observer_list, &mock_observer2);
+  DispatchPendingEvents(observer_list);
+  EXPECT_EQ(event, mock_observer1.LastEvent());
+  EXPECT_EQ(event, mock_observer2.LastEvent());
+  EXPECT_EQ(2, mock_observer1.EventCount());
+  EXPECT_EQ(2, mock_observer2.EventCount());
+  EXPECT_EQ(NULL, observer_list.GetPendingEvent());
+  EXPECT_EQ(0, observer_list.GetRequiredUpdatesCount());
+}
+
+// Ensure that the |origin| field in events match the origin specified by the
+// observer on registration.
+TEST_F(StorageObserverListTest, ReplaceEventOrigin) {
+  StorageObserver::MonitorParams params(kStorageTypePersistent,
+                                        GURL(kDefaultOrigin),
+                                        2000, false);
+  MockObserver mock_observer;
+  StorageObserverList observer_list;
+  observer_list.AddObserver(&mock_observer, params);
+
+  StorageObserver::Event dispatched_event;
+  dispatched_event.filter = params.filter;
+  dispatched_event.filter.origin = GURL("https://www.foo.com/bar");
+  observer_list.OnStorageChange(dispatched_event);
+
+  EXPECT_EQ(params.filter.origin, mock_observer.LastEvent().filter.origin);
+}
+
+// Tests for HostStorageObservers:
+
+typedef StorageTestBase HostStorageObserversTest;
+
+// Verify that HostStorageObservers is initialized after the first usage change.
+TEST_F(HostStorageObserversTest, InitializeOnUsageChange) {
+  StorageObserver::MonitorParams params(kStorageTypePersistent,
+                                        GURL(kDefaultOrigin),
+                                        2000, false);
+  const int64 kUsage = 324554;
+  const int64 kQuota = 234354354;
+  quota_manager_->SetCallbackParams(kUsage, kQuota, kQuotaStatusOk);
+
+  MockObserver mock_observer;
+  HostStorageObservers host_observers(quota_manager_.get());
+  host_observers.AddObserver(&mock_observer, params);
+
+  // Verify that HostStorageObservers dispatches the first event correctly.
+  StorageObserver::Event expected_event(params.filter, kUsage, kQuota);
+  host_observers.NotifyUsageChange(params.filter, 87324);
+  EXPECT_EQ(expected_event, mock_observer.LastEvent());
+  EXPECT_EQ(1, mock_observer.EventCount());
+  EXPECT_TRUE(host_observers.is_initialized());
+
+  // Verify that HostStorageObservers handles subsequent usage changes
+  // correctly.
+  const int64 kDelta = 2345;
+  expected_event.usage += kDelta;
+  SetLastNotificationTime(host_observers, &mock_observer);
+  host_observers.NotifyUsageChange(params.filter, kDelta);
+  EXPECT_EQ(expected_event, mock_observer.LastEvent());
+  EXPECT_EQ(2, mock_observer.EventCount());
+}
+
+// Verify that HostStorageObservers is initialized after the adding the first
+// observer that elected to receive the initial state.
+TEST_F(HostStorageObserversTest, InitializeOnObserver) {
+  const int64 kUsage = 74387;
+  const int64 kQuota = 92834743;
+  quota_manager_->SetCallbackParams(kUsage, kQuota, kQuotaStatusOk);
+  HostStorageObservers host_observers(quota_manager_.get());
+
+  // |host_observers| should not be initialized after the first observer is
+  // added because it did not elect to receive the initial state.
+  StorageObserver::MonitorParams params(kStorageTypePersistent,
+                                        GURL(kDefaultOrigin),
+                                        2000, false);
+  MockObserver mock_observer1;
+  host_observers.AddObserver(&mock_observer1, params);
+  EXPECT_FALSE(host_observers.is_initialized());
+  EXPECT_EQ(0, mock_observer1.EventCount());
+
+  // |host_observers| should be initialized after the second observer is
+  // added.
+  MockObserver mock_observer2;
+  params.dispatch_initial_state = true;
+  host_observers.AddObserver(&mock_observer2, params);
+  StorageObserver::Event expected_event(params.filter, kUsage, kQuota);
+  EXPECT_EQ(expected_event, mock_observer2.LastEvent());
+  EXPECT_EQ(0, mock_observer1.EventCount());
+  EXPECT_EQ(1, mock_observer2.EventCount());
+  EXPECT_TRUE(host_observers.is_initialized());
+  EXPECT_EQ(NULL, host_observers.GetPendingEvent());
+  EXPECT_EQ(0, host_observers.GetRequiredUpdatesCount());
+
+  // Verify that both observers will receive events after a usage change.
+  const int64 kDelta = 2345;
+  expected_event.usage += kDelta;
+  SetLastNotificationTime(host_observers, &mock_observer2);
+  host_observers.NotifyUsageChange(params.filter, kDelta);
+  EXPECT_EQ(expected_event, mock_observer1.LastEvent());
+  EXPECT_EQ(expected_event, mock_observer2.LastEvent());
+  EXPECT_EQ(1, mock_observer1.EventCount());
+  EXPECT_EQ(2, mock_observer2.EventCount());
+  EXPECT_EQ(NULL, host_observers.GetPendingEvent());
+  EXPECT_EQ(0, host_observers.GetRequiredUpdatesCount());
+
+  // Verify that the addition of a third observer only causes an event to be
+  // dispatched to the new observer.
+  MockObserver mock_observer3;
+  params.dispatch_initial_state = true;
+  host_observers.AddObserver(&mock_observer3, params);
+  EXPECT_EQ(1, mock_observer1.EventCount());
+  EXPECT_EQ(2, mock_observer2.EventCount());
+  EXPECT_EQ(1, mock_observer3.EventCount());
+  EXPECT_EQ(expected_event, mock_observer3.LastEvent());
+}
+
+// Verify that negative usage and quota is changed to zero.
+TEST_F(HostStorageObserversTest, NegativeUsageAndQuota) {
+  StorageObserver::MonitorParams params(kStorageTypePersistent,
+                                        GURL(kDefaultOrigin),
+                                        2000, false);
+  const int64 kUsage = -324554;
+  const int64 kQuota = -234354354;
+  quota_manager_->SetCallbackParams(kUsage, kQuota, kQuotaStatusOk);
+
+  MockObserver mock_observer;
+  HostStorageObservers host_observers(quota_manager_.get());
+  host_observers.AddObserver(&mock_observer, params);
+
+  StorageObserver::Event expected_event(params.filter, 0, 0);
+  host_observers.NotifyUsageChange(params.filter, -87324);
+  EXPECT_EQ(expected_event, mock_observer.LastEvent());
+}
+
+// Verify that HostStorageObservers can recover from a bad initialization.
+TEST_F(HostStorageObserversTest, RecoverFromBadUsageInit) {
+  StorageObserver::MonitorParams params(kStorageTypePersistent,
+                                        GURL(kDefaultOrigin),
+                                        2000, false);
+  MockObserver mock_observer;
+  HostStorageObservers host_observers(quota_manager_.get());
+  host_observers.AddObserver(&mock_observer, params);
+
+  // Set up the quota manager to return an error status.
+  const int64 kUsage = 6656;
+  const int64 kQuota = 99585556;
+  quota_manager_->SetCallbackParams(kUsage, kQuota, kQuotaErrorNotSupported);
+
+  // Verify that |host_observers| is not initialized and an event has not been
+  // dispatched.
+  host_observers.NotifyUsageChange(params.filter, 9438);
+  EXPECT_EQ(0, mock_observer.EventCount());
+  EXPECT_FALSE(host_observers.is_initialized());
+  EXPECT_EQ(NULL, host_observers.GetPendingEvent());
+  EXPECT_EQ(0, host_observers.GetRequiredUpdatesCount());
+
+  // Now ensure that quota manager returns a good status.
+  quota_manager_->SetCallbackParams(kUsage, kQuota, kQuotaStatusOk);
+  host_observers.NotifyUsageChange(params.filter, 9048543);
+  StorageObserver::Event expected_event(params.filter, kUsage, kQuota);
+  EXPECT_EQ(expected_event, mock_observer.LastEvent());
+  EXPECT_EQ(1, mock_observer.EventCount());
+  EXPECT_TRUE(host_observers.is_initialized());
+}
+
+// Tests for StorageTypeObservers:
+
+typedef StorageTestBase StorageTypeObserversTest;
+
+// Test adding and removing observers.
+TEST_F(StorageTypeObserversTest, AddRemoveObservers) {
+  StorageTypeObservers type_observers(quota_manager_.get());
+
+  StorageObserver::MonitorParams params1(kStorageTypePersistent,
+                                         GURL(kDefaultOrigin),
+                                         2000, false);
+  StorageObserver::MonitorParams params2(kStorageTypePersistent,
+                                         GURL(kAlternativeOrigin),
+                                         2000, false);
+  std::string host1 = net::GetHostOrSpecFromURL(params1.filter.origin);
+  std::string host2 = net::GetHostOrSpecFromURL(params2.filter.origin);
+
+  MockObserver mock_observer1;
+  MockObserver mock_observer2;
+  MockObserver mock_observer3;
+  type_observers.AddObserver(&mock_observer1, params1);
+  type_observers.AddObserver(&mock_observer2, params1);
+
+  type_observers.AddObserver(&mock_observer1, params2);
+  type_observers.AddObserver(&mock_observer2, params2);
+  type_observers.AddObserver(&mock_observer3, params2);
+
+  // Verify that the observers have been removed correctly.
+  ASSERT_TRUE(type_observers.GetHostObservers(host1));
+  ASSERT_TRUE(type_observers.GetHostObservers(host2));
+  EXPECT_EQ(2, type_observers.GetHostObservers(host1)->ObserverCount());
+  EXPECT_EQ(3, type_observers.GetHostObservers(host2)->ObserverCount());
+
+  // Remove an observer for a specific filter.
+  type_observers.RemoveObserverForFilter(&mock_observer1, params1.filter);
+  ASSERT_TRUE(type_observers.GetHostObservers(host1));
+  ASSERT_TRUE(type_observers.GetHostObservers(host2));
+  EXPECT_EQ(1, type_observers.GetHostObservers(host1)->ObserverCount());
+  EXPECT_EQ(3, type_observers.GetHostObservers(host2)->ObserverCount());
+
+  // Remove all instances of an observer.
+  type_observers.RemoveObserver(&mock_observer2);
+  ASSERT_TRUE(type_observers.GetHostObservers(host2));
+  EXPECT_EQ(2, type_observers.GetHostObservers(host2)->ObserverCount());
+  // Observers of host1 has been deleted as it is empty.
+  EXPECT_FALSE(type_observers.GetHostObservers(host1));
+}
+
+// Tests for StorageMonitor:
+
+class StorageMonitorTest : public StorageTestBase {
+ public:
+  StorageMonitorTest()
+      : storage_monitor_(NULL),
+        params1_(kStorageTypeTemporary,
+                 GURL(kDefaultOrigin),
+                 2000, false),
+        params2_(kStorageTypePersistent,
+                 GURL(kDefaultOrigin),
+                 2000, false) {
+  }
+
+ protected:
+  virtual void SetUp() OVERRIDE {
+    StorageTestBase::SetUp();
+
+    storage_monitor_ = quota_manager_->storage_monitor_.get();
+    host_ = net::GetHostOrSpecFromURL(params1_.filter.origin);
+
+    storage_monitor_->AddObserver(&mock_observer1_, params1_);
+    storage_monitor_->AddObserver(&mock_observer2_, params1_);
+
+    storage_monitor_->AddObserver(&mock_observer1_, params2_);
+    storage_monitor_->AddObserver(&mock_observer2_, params2_);
+    storage_monitor_->AddObserver(&mock_observer3_, params2_);
+  }
+
+  void CheckObserverCount(int expected_temporary, int expected_persistent) {
+    ASSERT_TRUE(storage_monitor_->GetStorageTypeObservers(
+                    kStorageTypeTemporary));
+    ASSERT_TRUE(storage_monitor_->GetStorageTypeObservers(
+                    kStorageTypeTemporary)->GetHostObservers(host_));
+    EXPECT_EQ(expected_temporary,
+              storage_monitor_->GetStorageTypeObservers(kStorageTypeTemporary)
+                  ->GetHostObservers(host_)->ObserverCount());
+
+    ASSERT_TRUE(storage_monitor_->GetStorageTypeObservers(
+                    kStorageTypePersistent));
+    ASSERT_TRUE(storage_monitor_->GetStorageTypeObservers(
+                    kStorageTypePersistent)->GetHostObservers(host_));
+    EXPECT_EQ(expected_persistent,
+              storage_monitor_->GetStorageTypeObservers(kStorageTypePersistent)
+                  ->GetHostObservers(host_)->ObserverCount());
+  }
+
+  StorageMonitor* storage_monitor_;
+  StorageObserver::MonitorParams params1_;
+  StorageObserver::MonitorParams params2_;
+  MockObserver mock_observer1_;
+  MockObserver mock_observer2_;
+  MockObserver mock_observer3_;
+  std::string host_;
+};
+
+// Test adding storage observers.
+TEST_F(StorageMonitorTest, AddObservers) {
+  // Verify that the observers are added correctly.
+  CheckObserverCount(2, 3);
+}
+
+// Test dispatching events to storage observers.
+TEST_F(StorageMonitorTest, EventDispatch) {
+  // Verify dispatch of events.
+  const int64 kUsage = 5325;
+  const int64 kQuota = 903845;
+  quota_manager_->SetCallbackParams(kUsage, kQuota, kQuotaStatusOk);
+  storage_monitor_->NotifyUsageChange(params1_.filter, 9048543);
+
+  StorageObserver::Event expected_event(params1_.filter, kUsage, kQuota);
+  EXPECT_EQ(1, mock_observer1_.EventCount());
+  EXPECT_EQ(1, mock_observer2_.EventCount());
+  EXPECT_EQ(0, mock_observer3_.EventCount());
+  EXPECT_EQ(expected_event, mock_observer1_.LastEvent());
+  EXPECT_EQ(expected_event, mock_observer2_.LastEvent());
+}
+
+// Test removing all instances of an observer.
+TEST_F(StorageMonitorTest, RemoveObserver) {
+  storage_monitor_->RemoveObserver(&mock_observer1_);
+  CheckObserverCount(1, 2);
+}
+
+// Test removing an observer for a specific filter.
+TEST_F(StorageMonitorTest, RemoveObserverForFilter) {
+  storage_monitor_->RemoveObserverForFilter(&mock_observer1_, params2_.filter);
+  CheckObserverCount(2, 2);
+}
+
+// Integration test for QuotaManager and StorageMonitor:
+
+class StorageMonitorIntegrationTest : public testing::Test {
+ public:
+  virtual void SetUp() OVERRIDE {
+    ASSERT_TRUE(data_dir_.CreateUniqueTempDir());
+    storage_policy_ = new MockSpecialStoragePolicy();
+    quota_manager_ = new QuotaManager(
+        false,
+        data_dir_.path(),
+        base::MessageLoopProxy::current().get(),
+        base::MessageLoopProxy::current().get(),
+        storage_policy_.get());
+
+    client_ = new MockStorageClient(quota_manager_->proxy(),
+                                    NULL,
+                                    QuotaClient::kFileSystem,
+                                    0);
+
+    quota_manager_->proxy()->RegisterClient(client_);
+  }
+
+  virtual void TearDown() OVERRIDE {
+    // This ensures the quota manager is destroyed correctly.
+    quota_manager_ = NULL;
+    base::RunLoop().RunUntilIdle();
+  }
+
+ protected:
+  base::MessageLoop message_loop_;
+  base::ScopedTempDir data_dir_;
+  scoped_refptr<MockSpecialStoragePolicy> storage_policy_;
+  scoped_refptr<QuotaManager> quota_manager_;
+  MockStorageClient* client_;
+};
+
+// This test simulates a usage change in a quota client and verifies that a
+// storage observer will receive a storage event.
+TEST_F(StorageMonitorIntegrationTest, NotifyUsageEvent) {
+  const StorageType kTestStorageType = kStorageTypePersistent;
+  const int64 kTestUsage = 234743;
+
+  // Register the observer.
+  StorageObserver::MonitorParams params(kTestStorageType,
+                                        GURL(kDefaultOrigin),
+                                        2000, false);
+  MockObserver mock_observer;
+  quota_manager_->AddStorageObserver(&mock_observer, params);
+
+  // Fire a usage change.
+  client_->AddOriginAndNotify(GURL(kDefaultOrigin),
+                              kTestStorageType,
+                              kTestUsage);
+  base::RunLoop().RunUntilIdle();
+
+  // Verify that the observer receives it.
+  ASSERT_EQ(1, mock_observer.EventCount());
+  const StorageObserver::Event& event = mock_observer.LastEvent();
+  EXPECT_EQ(params.filter, event.filter);
+  EXPECT_EQ(kTestUsage, event.usage);
+}
+
+}  // namespace quota