Add HistogramTester::GetAllSamples.

base/test/histogram_tester.h

 // 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 <ostream>
 #include <string>
+#include <utility>
+#include <vector>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_base.h"
 
 namespace base {
 
+struct Bucket;
 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();
@@ skipping 12 matching lines @@
   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;
 
+  // Returns a list of all of the buckets recorded since creation of this
+  // object, as vector<Bucket>, where the Bucket represents the min boundary of
+  // the bucket and the count of samples recorded to that bucket since creation.
+  //
+  // Example usage, using gMock:
+  //   EXPECT_THAT(histogram_tester.GetAllSamples("HistogramName"),
+  //               ElementsAre(Bucket(1, 5), Bucket(2, 10), Bucket(3, 5)));
+  //
+  // If you build the expected list programmatically, you can use ContainerEq:
+  //   EXPECT_THAT(histogram_tester.GetAllSamples("HistogramName"),
+  //               ContainerEq(expected_buckets));
+  //
+  // or EXPECT_EQ if you prefer not to depend on gMock, at the expense of a
+  // slightly less helpful failure message:
+  //   EXPECT_EQ(expected_buckets,
+  //             histogram_tester.GetAllSamples("HistogramName"));
+  std::vector<Bucket> GetAllSamples(const std::string& name);
+
   // 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,
                         const 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,
                        const 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);
 };
 
+struct Bucket {
+  Bucket(base::HistogramBase::Sample min, base::HistogramBase::Count count)
+      : min(min), count(count) {}
+
+  bool operator==(const Bucket& other) const;
+
+  base::HistogramBase::Sample min;
+  base::HistogramBase::Count count;
+};
+
+void PrintTo(const Bucket& value, std::ostream* os);
+
 }  // namespace base
 
 #endif  // BASE_TEST_HISTOGRAM_TESTER_H_