base/test/histogram_tester.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/test/histogram_tester.h"
   6
   7 #include "base/metrics/histogram.h"
   8 #include "base/metrics/histogram_samples.h"
   9 #include "base/metrics/sample_map.h"
  10 #include "base/metrics/statistics_recorder.h"
  11 #include "base/stl_util.h"
  12 #include "testing/gtest/include/gtest/gtest.h"
  13
  14 namespace base {
  15
  16 HistogramTester::HistogramTester() {
  17   StatisticsRecorder::Initialize();  // Safe to call multiple times.
  18
  19   // Record any histogram data that exists when the object is created so it can
  20   // be subtracted later.
  21   StatisticsRecorder::Histograms histograms;
  22   StatisticsRecorder::GetSnapshot(std::string(), &histograms);
  23   for (size_t i = 0; i < histograms.size(); ++i) {
  24     histograms_snapshot_[histograms[i]->histogram_name()] =
  25         histograms[i]->SnapshotSamples().release();
  26   }
  27 }
  28
  29 HistogramTester::~HistogramTester() {
  30   STLDeleteValues(&histograms_snapshot_);
  31 }
  32
  33 void HistogramTester::ExpectUniqueSample(
  34     const std::string& name,
  35     base::HistogramBase::Sample sample,
  36     base::HistogramBase::Count expected_count) const {
  37   base::HistogramBase* histogram =
  38       base::StatisticsRecorder::FindHistogram(name);
  39   EXPECT_NE(static_cast<base::HistogramBase*>(NULL), histogram)
  40       << "Histogram \"" << name << "\" does not exist.";
  41
  42   if (histogram) {
  43     scoped_ptr<base::HistogramSamples> samples(histogram->SnapshotSamples());
  44     CheckBucketCount(name, sample, expected_count, *samples);
  45     CheckTotalCount(name, expected_count, *samples);
  46   }
  47 }
  48
  49 void HistogramTester::ExpectBucketCount(
  50     const std::string& name,
  51     base::HistogramBase::Sample sample,
  52     base::HistogramBase::Count expected_count) const {
  53   base::HistogramBase* histogram =
  54       base::StatisticsRecorder::FindHistogram(name);
  55   EXPECT_NE(static_cast<base::HistogramBase*>(NULL), histogram)
  56       << "Histogram \"" << name << "\" does not exist.";
  57
  58   if (histogram) {
  59     scoped_ptr<base::HistogramSamples> samples(histogram->SnapshotSamples());
  60     CheckBucketCount(name, sample, expected_count, *samples);
  61   }
  62 }
  63
  64 void HistogramTester::ExpectTotalCount(const std::string& name,
  65                                        base::HistogramBase::Count count) const {
  66   base::HistogramBase* histogram =
  67       base::StatisticsRecorder::FindHistogram(name);
  68   if (histogram) {
  69     scoped_ptr<base::HistogramSamples> samples(histogram->SnapshotSamples());
  70     CheckTotalCount(name, count, *samples);
  71   } else {
  72     // No histogram means there were zero samples.
  73     EXPECT_EQ(count, 0) << "Histogram \"" << name << "\" does not exist.";
  74   }
  75 }
  76
  77 std::vector<Bucket> HistogramTester::GetAllSamples(
  78     const std::string& name) const {
  79   std::vector<Bucket> samples;
  80   scoped_ptr<HistogramSamples> snapshot =
  81       GetHistogramSamplesSinceCreation(name);
  82   for (auto it = snapshot->Iterator(); !it->Done(); it->Next()) {
  83     HistogramBase::Sample sample;
  84     HistogramBase::Count count;
  85     it->Get(&sample, nullptr, &count);
  86     samples.push_back(Bucket(sample, count));
  87   }
  88   return samples;
  89 }
  90
  91 HistogramTester::CountsMap HistogramTester::GetTotalCountsForPrefix(
  92     const std::string& query) const {
  93   EXPECT_TRUE(query.find('.') != std::string::npos)
  94       << "|query| ought to contain at least one period, to avoid matching too"
  95       << " many histograms.";
  96
  97   // Find matches by using the prefix-matching logic built into GetSnapshot().
  98   StatisticsRecorder::Histograms query_matches;
  99   StatisticsRecorder::GetSnapshot(query, &query_matches);
 100
 101   CountsMap result;
 102   for (base::HistogramBase* histogram : query_matches) {
 103     scoped_ptr<HistogramSamples> new_samples =
 104         GetHistogramSamplesSinceCreation(histogram->histogram_name());
 105     // Omit unchanged histograms from the result.
 106     if (new_samples->TotalCount()) {
 107       result[histogram->histogram_name()] = new_samples->TotalCount();
 108     }
 109   }
 110   return result;
 111 }
 112
 113 scoped_ptr<HistogramSamples> HistogramTester::GetHistogramSamplesSinceCreation(
 114     const std::string& histogram_name) const {
 115   HistogramBase* histogram = StatisticsRecorder::FindHistogram(histogram_name);
 116   // Whether the histogram exists or not may not depend on the current test
 117   // calling this method, but rather on which tests ran before and possibly
 118   // generated a histogram or not (see http://crbug.com/473689). To provide a
 119   // response which is independent of the previously run tests, this method
 120   // creates empty samples in the absence of the histogram, rather than
 121   // returning null.
 122   if (!histogram)
 123     return scoped_ptr<HistogramSamples>(new SampleMap);
 124   scoped_ptr<HistogramSamples> named_samples(histogram->SnapshotSamples());
 125   auto original_samples_it = histograms_snapshot_.find(histogram_name);
 126   if (original_samples_it != histograms_snapshot_.end())
 127     named_samples->Subtract(*original_samples_it->second);
 128   return named_samples.Pass();
 129 }
 130
 131 void HistogramTester::CheckBucketCount(
 132     const std::string& name,
 133     base::HistogramBase::Sample sample,
 134     base::HistogramBase::Count expected_count,
 135     const base::HistogramSamples& samples) const {
 136   int actual_count = samples.GetCount(sample);
 137   std::map<std::string, HistogramSamples*>::const_iterator histogram_data;
 138   histogram_data = histograms_snapshot_.find(name);
 139   if (histogram_data != histograms_snapshot_.end())
 140     actual_count -= histogram_data->second->GetCount(sample);
 141
 142   EXPECT_EQ(expected_count, actual_count)
 143       << "Histogram \"" << name
 144       << "\" does not have the right number of samples (" << expected_count
 145       << ") in the expected bucket (" << sample << "). It has (" << actual_count
 146       << ").";
 147 }
 148
 149 void HistogramTester::CheckTotalCount(
 150     const std::string& name,
 151     base::HistogramBase::Count expected_count,
 152     const base::HistogramSamples& samples) const {
 153   int actual_count = samples.TotalCount();
 154   std::map<std::string, HistogramSamples*>::const_iterator histogram_data;
 155   histogram_data = histograms_snapshot_.find(name);
 156   if (histogram_data != histograms_snapshot_.end())
 157     actual_count -= histogram_data->second->TotalCount();
 158
 159   EXPECT_EQ(expected_count, actual_count)
 160       << "Histogram \"" << name
 161       << "\" does not have the right total number of samples ("
 162       << expected_count << "). It has (" << actual_count << ").";
 163 }
 164
 165 bool Bucket::operator==(const Bucket& other) const {
 166   return min == other.min && count == other.count;
 167 }
 168
 169 void PrintTo(const Bucket& bucket, std::ostream* os) {
 170   *os << "Bucket " << bucket.min << ": " << bucket.count;
 171 }
 172
 173 }  // namespace base