Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

base/test/histogram_tester_unittest.cc

+// 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 "base/test/histogram_tester.h"
+
+#include "base/memory/scoped_ptr.h"
+#include "base/metrics/histogram.h"
+#include "base/metrics/histogram_samples.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+
+const std::string kHistogram1 = "Test1";
+const std::string kHistogram2 = "Test2";
+const std::string kHistogram3 = "Test3";
+
+typedef testing::Test HistogramTesterTest;
+
+TEST_F(HistogramTesterTest, Scope) {
+  // Record a histogram before the creation of the recorder.
+  UMA_HISTOGRAM_BOOLEAN(kHistogram1, true);
+
+  HistogramTester tester;
+
+  // Verify that no histogram is recorded.
+  scoped_ptr<HistogramSamples> samples(
+      tester.GetHistogramSamplesSinceCreation(kHistogram1));
+  EXPECT_FALSE(samples);
+
+  // Record a histogram after the creation of the recorder.
+  UMA_HISTOGRAM_BOOLEAN(kHistogram1, true);
+
+  // Verify that one histogram is recorded.
+  samples = tester.GetHistogramSamplesSinceCreation(kHistogram1);
+  EXPECT_TRUE(samples);
+  EXPECT_EQ(1, samples->TotalCount());
+}
+
+TEST_F(HistogramTesterTest, TestUniqueSample) {
+  HistogramTester tester;
+
+  // Record into a sample thrice
+  UMA_HISTOGRAM_COUNTS_100(kHistogram1, 2);
+  UMA_HISTOGRAM_COUNTS_100(kHistogram1, 2);
+  UMA_HISTOGRAM_COUNTS_100(kHistogram1, 2);
+
+  tester.ExpectUniqueSample(kHistogram1, 2, 3);
+}
+
+TEST_F(HistogramTesterTest, TestBucketsSample) {
+  HistogramTester tester;
+
+  // Record into a sample twice
+  UMA_HISTOGRAM_COUNTS_100(kHistogram1, 2);
+  UMA_HISTOGRAM_COUNTS_100(kHistogram1, 2);
+  UMA_HISTOGRAM_COUNTS_100(kHistogram1, 2);
+  UMA_HISTOGRAM_COUNTS_100(kHistogram1, 2);
+  UMA_HISTOGRAM_COUNTS_100(kHistogram1, 3);
+
+  tester.ExpectBucketCount(kHistogram1, 2, 4);
+  tester.ExpectBucketCount(kHistogram1, 3, 1);
+
+  tester.ExpectTotalCount(kHistogram1, 6);
+}
+
+TEST_F(HistogramTesterTest, TestBucketsSampleWithScope) {
+  // Record into a sample twice, once before the tester creation and once after.
+  UMA_HISTOGRAM_COUNTS_100(kHistogram1, 2);
+
+  HistogramTester tester;
+  UMA_HISTOGRAM_COUNTS_100(kHistogram1, 3);
+
+  tester.ExpectBucketCount(kHistogram1, 2, 0);
+  tester.ExpectBucketCount(kHistogram1, 3, 1);
+
+  tester.ExpectTotalCount(kHistogram1, 1);
+}
+
+}  // namespace base