Adding UMA to PreviewsDataSavings

components/previews/previews_data_savings_unittest.cc

Index: components/previews/previews_data_savings_unittest.cc
diff --git a/components/previews/previews_data_savings_unittest.cc b/components/previews/previews_data_savings_unittest.cc
index 6dbba267e1c86e7af214a707c55d66c0c339996c..dbc37b6d0e2e9eda31fefb97d44578087f63a05d 100644
--- a/components/previews/previews_data_savings_unittest.cc
+++ b/components/previews/previews_data_savings_unittest.cc
@@ -2,20 +2,21 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/previews/previews_data_savings.h"
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 
+#include "base/test/histogram_tester.h"
 #include "components/data_reduction_proxy/core/common/data_savings_recorder.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace previews {
 
 namespace {
 
 class TestDataSavingsRecorder
     : public data_reduction_proxy::DataSavingsRecorder {
  public:
@@ -62,39 +63,104 @@ class PreviewsDataSavingsTest : public testing::Test {
         data_savings_(
             new PreviewsDataSavings(test_data_savings_recorder_.get())) {}
   ~PreviewsDataSavingsTest() override {}
 
   PreviewsDataSavings* data_savings() const { return data_savings_.get(); }
 
   TestDataSavingsRecorder* test_data_savings_recorder() const {
     return test_data_savings_recorder_.get();
   }
 
+  base::HistogramTester* histogram_tester() { return &histogram_tester_; }
+
  private:
+  base::HistogramTester histogram_tester_;
+
   std::unique_ptr<TestDataSavingsRecorder> test_data_savings_recorder_;
   std::unique_ptr<PreviewsDataSavings> data_savings_;
 };
 
 TEST_F(PreviewsDataSavingsTest, RecordDataSavings) {
   int64_t original_size = 200;
   int64_t data_used = 100;
   std::string host = "host";
 
   EXPECT_EQ(0, test_data_savings_recorder()->data_used());
   EXPECT_EQ(0, test_data_savings_recorder()->original_size());
   test_data_savings_recorder()->set_data_saver_enabled(false);
-
   data_savings()->RecordDataSavings(host, data_used, original_size);
 
   EXPECT_EQ(0, test_data_savings_recorder()->data_used());
   EXPECT_EQ(0, test_data_savings_recorder()->original_size());
   EXPECT_EQ(std::string(), test_data_savings_recorder()->last_host());
-  test_data_savings_recorder()->set_data_saver_enabled(true);
 
+  test_data_savings_recorder()->set_data_saver_enabled(true);
   data_savings()->RecordDataSavings(host, data_used, original_size);
 
   EXPECT_EQ(data_used, test_data_savings_recorder()->data_used());
   EXPECT_EQ(original_size, test_data_savings_recorder()->original_size());
   EXPECT_EQ(host, test_data_savings_recorder()->last_host());
 }
 
+TEST_F(PreviewsDataSavingsTest, RecordDataSavingsHistograms) {
+  int64_t twenty_kb = 20480;
+  int64_t twenty = twenty_kb >> 10;
+  int64_t ten_kb = 10240;
+  int64_t ten = ten_kb >> 10;
+  std::string host = "host";
+
+  test_data_savings_recorder()->set_data_saver_enabled(false);
+  data_savings()->RecordDataSavings(host, ten_kb, twenty_kb);
+
+  // The histograms record bytes in KB.
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.OriginalContentLength.DataSaverDisabled", twenty, 1);
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.ContentLength.DataSaverDisabled", ten, 1);
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.DataSavings.DataSaverDisabled", twenty - ten, 1);
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.DataSavingsPercent.DataSaverDisabled",
+      (twenty_kb - ten_kb) * 100 / twenty_kb, 1);
+
+  data_savings()->RecordDataSavings(host, twenty_kb, ten_kb);
+
+  // The histograms record bytes in KB.
+  histogram_tester()->ExpectBucketCount(
+      "Previews.OriginalContentLength.DataSaverDisabled", ten, 1);
+  histogram_tester()->ExpectBucketCount(
+      "Previews.ContentLength.DataSaverDisabled", twenty, 1);
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.DataInflation.DataSaverDisabled", twenty - ten, 1);
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.DataInflationPercent.DataSaverDisabled",
+      (twenty_kb - ten_kb) * 100 / twenty_kb, 1);
+
+  test_data_savings_recorder()->set_data_saver_enabled(true);
+  data_savings()->RecordDataSavings(host, ten_kb, twenty_kb);
+
+  // The histograms record bytes in KB.
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.OriginalContentLength.DataSaverEnabled", twenty, 1);
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.ContentLength.DataSaverEnabled", ten, 1);
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.DataSavings.DataSaverEnabled", twenty - ten, 1);
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.DataSavingsPercent.DataSaverEnabled",
+      (twenty_kb - ten_kb) * 100 / twenty_kb, 1);
+
+  data_savings()->RecordDataSavings(host, twenty_kb, ten_kb);
+
+  // The histograms record bytes in KB.
+  histogram_tester()->ExpectBucketCount(
+      "Previews.OriginalContentLength.DataSaverEnabled", ten, 1);
+  histogram_tester()->ExpectBucketCount(
+      "Previews.ContentLength.DataSaverEnabled", twenty, 1);
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.DataInflation.DataSaverEnabled", twenty - ten, 1);
+  histogram_tester()->ExpectUniqueSample(
+      "Previews.DataInflationPercent.DataSaverEnabled",
+      (twenty_kb - ten_kb) * 100 / twenty_kb, 1);
+}
+
 }  // namespace previews