[NTP Snippets] Add metric for fetch error cases

components/ntp_snippets/ntp_snippets_fetcher_unittest.cc

 // Copyright 2016 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.
 
 #include "components/ntp_snippets/ntp_snippets_fetcher.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
+#include "base/test/histogram_tester.h"
 #include "base/thread_task_runner_handle.h"
 #include "google_apis/google_api_keys.h"
 #include "net/url_request/test_url_fetcher_factory.h"
 #include "net/url_request/url_request_test_util.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace ntp_snippets {
 namespace {
 
+using testing::ElementsAre;
 using testing::IsEmpty;
 using testing::IsNull;
 using testing::Not;
 using testing::NotNull;
 
 const char kTestContentSnippetsServerFormat[] =
     "https://chromereader-pa.googleapis.com/v1/fetch?key=%s";
 
 class MockSnippetsAvailableCallback {
  public:
@@ skipping 32 matching lines @@
 
   net::FakeURLFetcherFactory& fake_url_fetcher_factory() {
     return fake_url_fetcher_factory_;
   }
 
   NTPSnippetsFetcher& snippets_fetcher() { return snippets_fetcher_; }
   MockSnippetsAvailableCallback& mock_callback() { return mock_callback_; }
   void RunUntilIdle() { message_loop_.RunUntilIdle(); }
   const GURL& test_url() { return test_url_; }
 
+  base::HistogramTester& histogram_tester() { return histogram_tester_; }
+
  private:
   FailingFakeURLFetcherFactory failing_url_fetcher_factory_;
   // Instantiation of factory automatically sets itself as URLFetcher's factory.
   net::FakeURLFetcherFactory fake_url_fetcher_factory_;
   // Needed to use ThreadTaskRunnerHandle.
   base::MessageLoop message_loop_;
   NTPSnippetsFetcher snippets_fetcher_;
   MockSnippetsAvailableCallback mock_callback_;
   std::unique_ptr<
       NTPSnippetsFetcher::SnippetsAvailableCallbackList::Subscription>
       snippets_fetcher_subscription_;
   const GURL test_url_;
+  base::HistogramTester histogram_tester_;
 
   DISALLOW_COPY_AND_ASSIGN(NTPSnippetsFetcherTest);
 };
 
 TEST_F(NTPSnippetsFetcherTest, ShouldNotFetchOnCreation) {
   // The lack of registered baked in responses would cause any fetch to fail.
   RunUntilIdle();
+  EXPECT_THAT(histogram_tester().GetAllSamples(
+                  "NewTabPage.Snippets.FetchHttpResponseOrErrorCode"),
+              IsEmpty());
 }
 
 TEST_F(NTPSnippetsFetcherTest, ShouldFetchSuccessfully) {
   const std::string json_str = "{ \"recos\": [] }";
   fake_url_fetcher_factory().SetFakeResponse(test_url(),
                                              /*data=*/json_str, net::HTTP_OK,
                                              net::URLRequestStatus::SUCCESS);
   EXPECT_CALL(mock_callback(), Run(/*snippets_json=*/json_str,
                                    /*status_message=*/std::string()))
       .Times(1);
   snippets_fetcher().FetchSnippets(/*hosts=*/std::set<std::string>(),
                                    /*count=*/1);
   RunUntilIdle();
+  EXPECT_THAT(histogram_tester().GetAllSamples(
+                  "NewTabPage.Snippets.FetchHttpResponseOrErrorCode"),
+              ElementsAre(base::Bucket(/*min=*/200, /*count=*/1)));
 }
 
 TEST_F(NTPSnippetsFetcherTest, ShouldReportUrlStatusError) {
   fake_url_fetcher_factory().SetFakeResponse(test_url(),
                                              /*data=*/std::string(),
                                              net::HTTP_NOT_FOUND,
                                              net::URLRequestStatus::FAILED);
   EXPECT_CALL(mock_callback(),
               Run(/*snippets_json=*/std::string(),
                   /*status_message=*/"URLRequestStatus error -2"))
       .Times(1);
   snippets_fetcher().FetchSnippets(/*hosts=*/std::set<std::string>(),
                                    /*count=*/1);
   RunUntilIdle();
+  EXPECT_THAT(histogram_tester().GetAllSamples(
+                  "NewTabPage.Snippets.FetchHttpResponseOrErrorCode"),
+              ElementsAre(base::Bucket(/*min=*/-2, /*count=*/1)));
 }
 
 TEST_F(NTPSnippetsFetcherTest, ShouldReportHttpError) {
   fake_url_fetcher_factory().SetFakeResponse(test_url(),
                                              /*data=*/std::string(),
                                              net::HTTP_NOT_FOUND,
                                              net::URLRequestStatus::SUCCESS);
   EXPECT_CALL(mock_callback(), Run(/*snippets_json=*/std::string(),
                                    /*status_message=*/"HTTP error 404"))
       .Times(1);
   snippets_fetcher().FetchSnippets(/*hosts=*/std::set<std::string>(),
                                    /*count=*/1);
   RunUntilIdle();
+  EXPECT_THAT(histogram_tester().GetAllSamples(
+                  "NewTabPage.Snippets.FetchHttpResponseOrErrorCode"),
+              ElementsAre(base::Bucket(/*min=*/404, /*count=*/1)));
 }
 
 // This test actually verifies that the test setup itself is sane, to prevent
 // hard-to-reproduce test failures.
 TEST_F(NTPSnippetsFetcherTest, ShouldReportHttpErrorForMissingBakedResponse) {
   EXPECT_CALL(mock_callback(), Run(/*snippets_json=*/std::string(),
                                    /*status_message=*/Not(IsEmpty())))
       .Times(1);
   snippets_fetcher().FetchSnippets(/*hosts=*/std::set<std::string>(),
                                    /*count=*/1);
   RunUntilIdle();
 }
 
 TEST_F(NTPSnippetsFetcherTest, ShouldCancelOngoingFetch) {
   const std::string json_str = "{ \"recos\": [] }";
   fake_url_fetcher_factory().SetFakeResponse(test_url(),
                                              /*data=*/json_str, net::HTTP_OK,
                                              net::URLRequestStatus::SUCCESS);
   EXPECT_CALL(mock_callback(), Run(/*snippets_json=*/json_str,
                                    /*status_message=*/std::string()))
       .Times(1);
   snippets_fetcher().FetchSnippets(/*hosts=*/std::set<std::string>(),
                                    /*count=*/1);
   // Second call to FetchSnippets() overrides/cancels the previous. Callback is
   // expected to be called once.
   snippets_fetcher().FetchSnippets(/*hosts=*/std::set<std::string>(),
                                    /*count=*/1);
   RunUntilIdle();
+  EXPECT_THAT(histogram_tester().GetAllSamples(
+                  "NewTabPage.Snippets.FetchHttpResponseOrErrorCode"),
+              ElementsAre(base::Bucket(/*min=*/200, /*count=*/1)));
 }
 
 }  // namespace
 }  // namespace ntp_snippets