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// 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.
#ifndef BASE_TEST_HISTOGRAM_TESTER_H_
#define BASE_TEST_HISTOGRAM_TESTER_H_
#include <map>
#include <string>
#include "base/basictypes.h"
#include "base/memory/scoped_ptr.h"
#include "base/metrics/histogram.h"
#include "base/metrics/histogram_base.h"
namespace base {
class HistogramSamples;
// HistogramTester provides a simple interface for examining histograms, UMA
// or otherwise. Tests can use this interface to verify that histogram data is
// getting logged as intended.
class HistogramTester {
public:
// The constructor will call StatisticsRecorder::Initialize() for you. Also,
// this takes a snapshot of all current histograms counts.
HistogramTester();
~HistogramTester();
// We know the exact number of samples in a bucket, and that no other bucket
// should have samples. Measures the diff from the snapshot taken when this
// object was constructed.
void ExpectUniqueSample(const std::string& name,
base::HistogramBase::Sample sample,
base::HistogramBase::Count expected_count) const;
// We know the exact number of samples in a bucket, but other buckets may
// have samples as well. Measures the diff from the snapshot taken when this
// object was constructed.
void ExpectBucketCount(const std::string& name,
base::HistogramBase::Sample sample,
base::HistogramBase::Count expected_count) const;
// We don't know the values of the samples, but we know how many there are.
// This measures the diff from the snapshot taken when this object was
// constructed.
void ExpectTotalCount(const std::string& name,
base::HistogramBase::Count count) const;
// Access a modified HistogramSamples containing only what has been logged
// to the histogram since the creation of this object.
scoped_ptr<HistogramSamples> GetHistogramSamplesSinceCreation(
const std::string& histogram_name);
private:
// Verifies and asserts that value in the |sample| bucket matches the
// |expected_count|. The bucket's current value is determined from |samples|
// and is modified based on the snapshot stored for histogram |name|.
void CheckBucketCount(const std::string& name,
base::HistogramBase::Sample sample,
base::Histogram::Count expected_count,
base::HistogramSamples& samples) const;
// Verifies that the total number of values recorded for the histogram |name|
// is |expected_count|. This is checked against |samples| minus the snapshot
// that was taken for |name|.
void CheckTotalCount(const std::string& name,
base::Histogram::Count expected_count,
base::HistogramSamples& samples) const;
// Used to determine the histogram changes made during this instance's
// lifecycle. This instance takes ownership of the samples, which are deleted
// when the instance is destroyed.
std::map<std::string, HistogramSamples*> histograms_snapshot_;
DISALLOW_COPY_AND_ASSIGN(HistogramTester);
};
} // namespace base
#endif // BASE_TEST_HISTOGRAM_TESTER_H_
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