Create and integrate a metrics service client into Blimp engine.

blimp/engine/app/blimp_metrics_service_client_unittest.cc

+// Copyright 2016 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 "blimp/engine/app/blimp_metrics_service_client.h"
+
+#include <list>
+#include <string>
+
+#include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
+#include "base/test/test_simple_task_runner.h"
+#include "base/thread_task_runner_handle.h"
+#include "components/metrics/metrics_service.h"
+#include "components/pref_registry/pref_registry_syncable.h"
+#include "components/prefs/in_memory_pref_store.h"
+#include "components/prefs/pref_service.h"
+#include "components/prefs/pref_service_factory.h"
+#include "net/url_request/url_request_context_getter.h"
+#include "net/url_request/url_request_test_util.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace blimp {
+namespace engine {
+// Shows notifications which correspond to PersistentPrefStore's reading errors.

[Wez, 2016/05/01 00:12:59]

This function just seems to be a no-op dummy used to Bind() into a read-error
callback, so suggest describing what it's actually used for here (to make clear
why we need a strange no-op function :) rather than what a real implementation
should do.

+void HandleReadError(PersistentPrefStore::PrefReadError error) {
+}
+
+class BlimpMetricsServiceClientTest : public testing::Test {
+ protected:
+  void Initialize();
+  void Finalize();

[Wez, 2016/05/01 00:12:59]

Why not override Setup() and Teardown() from testing::Test here?

+
+  void SetUpPrefRegistry();

[Wez, 2016/05/01 00:12:59]

micro-nit: I believe we normally capitalize "setup" as Setup, not SetUp.

+  void SetUpPrefService();
+  void SetUpRequestContextGetter();
+
+  base::MessageLoop message_loop_;
+  scoped_refptr<user_prefs::PrefRegistrySyncable> pref_registry_;
+  std::unique_ptr<PrefService> pref_service_;
+  scoped_refptr<net::URLRequestContextGetter> request_context_getter_;
+};
+
+void BlimpMetricsServiceClientTest::Initialize() {
+  SetUpPrefRegistry();
+  SetUpPrefService();
+  SetUpRequestContextGetter();
+  ASSERT_NE(nullptr, pref_service_.get());

[Wez, 2016/05/01 00:12:59]

Can you use ASSERT_TRUE(pref_service_) here?

+  base::SetRecordActionTaskRunner(message_loop_.task_runner());
+  InitializeBlimpMetrics(std::move(pref_service_), request_context_getter_);

[Wez, 2016/05/01 00:12:59]

Since you're passing the pref-service here, and creating it in the
SetUpPrefService() sub-routine, why not have the sub-routine return a
unique_ptr<> and avoid the need for the test-base-class member?

+  base::RunLoop().RunUntilIdle();
+}
+
+void BlimpMetricsServiceClientTest::Finalize() {
+  FinalizeBlimpMetrics();
+  base::RunLoop().RunUntilIdle();
+}
+
+void BlimpMetricsServiceClientTest::SetUpPrefRegistry() {
+  pref_registry_ = new user_prefs::PrefRegistrySyncable();
+  metrics::MetricsService::RegisterPrefs(pref_registry_.get());
+}
+
+void BlimpMetricsServiceClientTest::SetUpPrefService() {
+  PrefServiceFactory pref_service_factory;
+  pref_service_factory.set_user_prefs(new InMemoryPrefStore());
+  pref_service_factory.set_read_error_callback(base::Bind(&HandleReadError));
+  pref_service_ = pref_service_factory.Create(pref_registry_.get());
+}
+
+void BlimpMetricsServiceClientTest::SetUpRequestContextGetter() {
+  request_context_getter_ =
+      new net::TestURLRequestContextGetter(base::ThreadTaskRunnerHandle::Get());
+}
+
+TEST_F(BlimpMetricsServiceClientTest, InitializeFinalize) {
+  Initialize();
+
+  // TODO(jessicag): Check request_context_getter_ set.

[Wez, 2016/05/01 00:12:59]

Is this a reminder to just have ASSERT_TRUE(request_context_getter_), in effect?

+  // PrefService unique pointer moved to BlimpMetricsServiceClient.
+  EXPECT_EQ(nullptr, pref_service_.get());
+
+  // TODO(jessicag): Confirm registration of metrics providers.
+  // TODO(jessicag): MetricsService initializes recording state.
+  // TODO(jessicag): Confirm MetricsService::Start() is called.

[Wez, 2016/05/01 00:12:59]

If the MetricsService is too much of a black-box for us to be able to do this
fine-grained testing, can we at least do something like:

1. Verify that the pref-store is empty.
2. Log a metric.
3. Verify that the pref-store is no longer empty.

or maybe even verify that the pref-store has correct-looking content?

Remember that if we need additional hooks set by our MetricsServiceClient impl
then we can add an InitializeBlimpMetricsForTest helper.

+
+  Finalize();
+
+  // TODO(jessicag): Ensure MetricsService::Stop() is called.
+}
+
+}  // namespace engine
+}  // namespace blimp