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 #ifndef BASE_TEST_HISTOGRAM_TESTER_H_ 6 #define BASE_TEST_HISTOGRAM_TESTER_H_ 7 8 #include <map> 9 #include <string> 10 11 #include "base/basictypes.h" 12 #include "base/memory/scoped_ptr.h" 13 #include "base/metrics/histogram.h" 14 #include "base/metrics/histogram_base.h" 15 16 namespace base { 17 18 class HistogramSamples; 19 20 // HistogramTester provides a simple interface for examining histograms, UMA 21 // or otherwise. Tests can use this interface to verify that histogram data is 22 // getting logged as intended. 23 class HistogramTester { 24 public: 25 // The constructor will call StatisticsRecorder::Initialize() for you. Also, 26 // this takes a snapshot of all current histograms counts. 27 HistogramTester(); 28 ~HistogramTester(); 29 30 // We know the exact number of samples in a bucket, and that no other bucket 31 // should have samples. Measures the diff from the snapshot taken when this 32 // object was constructed. 33 void ExpectUniqueSample(const std::string& name, 34 base::HistogramBase::Sample sample, 35 base::HistogramBase::Count expected_count) const; 36 37 // We know the exact number of samples in a bucket, but other buckets may 38 // have samples as well. Measures the diff from the snapshot taken when this 39 // object was constructed. 40 void ExpectBucketCount(const std::string& name, 41 base::HistogramBase::Sample sample, 42 base::HistogramBase::Count expected_count) const; 43 44 // We don't know the values of the samples, but we know how many there are. 45 // This measures the diff from the snapshot taken when this object was 46 // constructed. 47 void ExpectTotalCount(const std::string& name, 48 base::HistogramBase::Count count) const; 49 50 // Access a modified HistogramSamples containing only what has been logged 51 // to the histogram since the creation of this object. 52 scoped_ptr<HistogramSamples> GetHistogramSamplesSinceCreation( 53 const std::string& histogram_name); 54 55 private: 56 // Verifies and asserts that value in the |sample| bucket matches the 57 // |expected_count|. The bucket's current value is determined from |samples| 58 // and is modified based on the snapshot stored for histogram |name|. 59 void CheckBucketCount(const std::string& name, 60 base::HistogramBase::Sample sample, 61 base::Histogram::Count expected_count, 62 base::HistogramSamples& samples) const; 63 64 // Verifies that the total number of values recorded for the histogram |name| 65 // is |expected_count|. This is checked against |samples| minus the snapshot 66 // that was taken for |name|. 67 void CheckTotalCount(const std::string& name, 68 base::Histogram::Count expected_count, 69 base::HistogramSamples& samples) const; 70 71 // Used to determine the histogram changes made during this instance's 72 // lifecycle. This instance takes ownership of the samples, which are deleted 73 // when the instance is destroyed. 74 std::map<std::string, HistogramSamples*> histograms_snapshot_; 75 76 DISALLOW_COPY_AND_ASSIGN(HistogramTester); 77 }; 78 79 } // namespace base 80 81 #endif // BASE_TEST_HISTOGRAM_TESTER_H_ 82