Add support for single sample metrics.

components/metrics/single_sample_metrics_factory_impl_unittest.cc

Index: components/metrics/single_sample_metrics_factory_impl_unittest.cc
diff --git a/components/metrics/single_sample_metrics_factory_impl_unittest.cc b/components/metrics/single_sample_metrics_factory_impl_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0ef75be789851849150efcea49c5b78823994600
--- /dev/null
+++ b/components/metrics/single_sample_metrics_factory_impl_unittest.cc
@@ -0,0 +1,183 @@
+// Copyright 2017 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 "components/metrics/single_sample_metrics_factory_impl.h"
+
+#include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
+#include "base/test/gtest_util.h"
+#include "base/test/histogram_tester.h"
+#include "base/threading/thread.h"
+#include "components/metrics/single_sample_metrics.h"
+#include "services/service_manager/public/cpp/bind_source_info.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace metrics {
+
+namespace {
+
+const base::HistogramBase::Sample kMin = 1;
+const base::HistogramBase::Sample kMax = 10;
+const uint32_t kBucketCount = 10;
+const char kMetricName[] = "Single.Sample.Metric";
+
+class SingleSampleMetricsFactoryImplTest : public testing::Test {
+ public:
+  SingleSampleMetricsFactoryImplTest() : thread_("TestThread") {
+    InitializeSingleSampleMetricsFactory(
+        base::BindRepeating(&SingleSampleMetricsFactoryImplTest::CreateProvider,
+                            base::Unretained(this)));
+    factory_ = static_cast<SingleSampleMetricsFactoryImpl*>(
+        base::SingleSampleMetricsFactory::Get());
+  }
+
+  ~SingleSampleMetricsFactoryImplTest() override {
+    factory_->DestroyProviderForTesting();
+    if (thread_.IsRunning()) {
+      thread_.task_runner()->PostTask(
+          FROM_HERE,
+          base::Bind(&SingleSampleMetricsFactoryImpl::DestroyProviderForTesting,
+                     base::Unretained(factory_)));
+      thread_.Stop();
+    }
+    base::SingleSampleMetricsFactory::DeleteFactoryForTesting();
+  }
+
+ protected:
+  void StartThread() { ASSERT_TRUE(thread_.Start()); }
+
+  void CreateProvider(mojom::SingleSampleMetricsProviderRequest request) {
+    CreateSingleSampleMetricsProvider(service_manager::BindSourceInfo(),
+                                      std::move(request));
+    provider_count_++;
+  }
+
+  std::unique_ptr<base::SingleSampleMetric> CreateMetricOnThread() {
+    std::unique_ptr<base::SingleSampleMetric> metric;
+    base::RunLoop run_loop;
+    thread_.task_runner()->PostTaskAndReply(
+        FROM_HERE,
+        base::Bind(&SingleSampleMetricsFactoryImplTest::CreateAndStoreMetric,
+                   base::Unretained(this), &metric),
+        run_loop.QuitClosure());
+    run_loop.Run();
+    return metric;
+  }
+
+  void CreateAndStoreMetric(std::unique_ptr<base::SingleSampleMetric>* metric) {
+    *metric = factory_->CreateCustomCountsMetric(kMetricName, kMin, kMax,
+                                                 kBucketCount);
+  }
+
+  base::MessageLoop message_looqp_;
+  SingleSampleMetricsFactoryImpl* factory_;
+  base::Thread thread_;
+  size_t provider_count_ = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SingleSampleMetricsFactoryImplTest);
+};
+
+}  // namespace
+
+TEST_F(SingleSampleMetricsFactoryImplTest, SingleProvider) {
+  std::unique_ptr<base::SingleSampleMetric> metric1 =
+      factory_->CreateCustomCountsMetric(kMetricName, kMin, kMax, kBucketCount);
+
+  std::unique_ptr<base::SingleSampleMetric> metric2 =
+      factory_->CreateCustomCountsMetric(kMetricName, kMin, kMax, kBucketCount);
+
+  // Verify that only a single provider is created for multiple metrics.
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(1u, provider_count_);
+}
+
+TEST_F(SingleSampleMetricsFactoryImplTest, DoesNothing) {
+  base::HistogramTester tester;
+
+  std::unique_ptr<base::SingleSampleMetric> metric =
+      factory_->CreateCustomCountsMetric(kMetricName, kMin, kMax, kBucketCount);
+  metric.reset();
+
+  // Verify that no sample is recorded if SetSample() is never called.
+  base::RunLoop().RunUntilIdle();
+  tester.ExpectTotalCount(kMetricName, 0);
+}
+
+TEST_F(SingleSampleMetricsFactoryImplTest, DefaultSingleSampleMetricWithValue) {
+  base::HistogramTester tester;
+  std::unique_ptr<base::SingleSampleMetric> metric =
+      factory_->CreateCustomCountsMetric(kMetricName, kMin, kMax, kBucketCount);
+
+  const base::HistogramBase::Sample kLastSample = 9;
+  metric->SetSample(1);
+  metric->SetSample(3);
+  metric->SetSample(5);
+  metric->SetSample(kLastSample);
+  metric.reset();
+
+  // Verify only the last sample sent to SetSample() is recorded.
+  base::RunLoop().RunUntilIdle();
+  tester.ExpectUniqueSample(kMetricName, kLastSample, 1);
+
+  // Verify construction implicitly by requesting a histogram with the same
+  // parameters; this test relies on the fact that histogram objects are unique
+  // per name. Different parameters will result in a nullptr being returned.
+  EXPECT_FALSE(base::Histogram::FactoryGet(kMetricName, 1, 3, 3,
+                                           base::HistogramBase::kNoFlags));
+  EXPECT_TRUE(base::Histogram::FactoryGet(
+      kMetricName, kMin, kMax, kBucketCount,
+      base::HistogramBase::kUmaTargetedHistogramFlag));
+}
+
+TEST_F(SingleSampleMetricsFactoryImplTest, MultithreadedMetrics) {
+  base::HistogramTester tester;
+  std::unique_ptr<base::SingleSampleMetric> metric =
+      factory_->CreateCustomCountsMetric(kMetricName, kMin, kMax, kBucketCount);
+  EXPECT_EQ(1u, provider_count_);
+
+  StartThread();
+
+  std::unique_ptr<base::SingleSampleMetric> threaded_metric =
+      CreateMetricOnThread();
+  ASSERT_TRUE(threaded_metric);
+
+  // A second provider should be created to handle requests on our new thread.
+  EXPECT_EQ(2u, provider_count_);
+
+  // Calls from the wrong thread should DCHECK.
+  EXPECT_DCHECK_DEATH(threaded_metric->SetSample(5));
+  EXPECT_DCHECK_DEATH(threaded_metric.reset());
+
+  // Test that samples are set on each thread correctly.
+  const base::HistogramBase::Sample kSample = 7;
+
+  {
+    metric->SetSample(kSample);
+
+    base::RunLoop run_loop;
+    thread_.task_runner()->PostTaskAndReply(
+        FROM_HERE,
+        base::Bind(&base::SingleSampleMetric::SetSample,
+                   base::Unretained(threaded_metric.get()), kSample),
+        run_loop.QuitClosure());
+    run_loop.Run();
+  }
+
+  // Release metrics and cycle threads to ensure destruction completes.
+  {
+    thread_.task_runner()->DeleteSoon(FROM_HERE, threaded_metric.release());
+
+    base::RunLoop run_loop;
+    thread_.task_runner()->PostTaskAndReply(
+        FROM_HERE, base::Bind(&base::DoNothing), run_loop.QuitClosure());
+    run_loop.Run();
+  }
+
+  metric.reset();
+  base::RunLoop().RunUntilIdle();
+  tester.ExpectUniqueSample(kMetricName, kSample, 2);
+}
+
+}  // namespace metrics