RemoteContentSuggestions: Stores the time of the last successful background fetch in a pref

components/ntp_snippets/remote/remote_suggestions_provider_unittest.cc

 // Copyright 2015 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/remote/remote_suggestions_provider.h"
 
 #include <memory>
 #include <utility>
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/json/json_reader.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/test/histogram_tester.h"
+#include "base/test/simple_test_tick_clock.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "components/image_fetcher/image_decoder.h"
 #include "components/image_fetcher/image_fetcher.h"
 #include "components/image_fetcher/image_fetcher_delegate.h"
 #include "components/ntp_snippets/category_factory.h"
 #include "components/ntp_snippets/category_info.h"
 #include "components/ntp_snippets/ntp_snippets_constants.h"
 #include "components/ntp_snippets/pref_names.h"
 #include "components/ntp_snippets/remote/ntp_snippet.h"
@@ skipping 1553 matching lines @@
     suggestions.push_back(GetSnippetWithUrl(
         base::StringPrintf("http://localhost/snippet-id-%d", i)));
   }
   LoadFromJSONString(service.get(), GetTestJson(suggestions));
   // TODO(tschumann): We should probably trim out any additional results and
   // only serve the MaxSnippetCount items.
   EXPECT_THAT(service->GetSnippetsForTesting(articles_category()),
               SizeIs(service->GetMaxSnippetCountForTesting() + 1));
 }
 
+TEST_F(RemoteSuggestionsProviderTest, StoreLastSuccessfullBackgroundFetchTime) {
+  // On initialization of the RemoteSuggestionsProvider a background fetch is
+  // triggered since the snippets DB is empty. Therefore the service must not be
+  // initialized until the test clock is set.
+  auto service = MakeSnippetsServiceWithoutInitialization();
+
+  auto simple_test_tick_clock = base::MakeUnique<base::SimpleTestTickClock>();
+  base::SimpleTestTickClock* simple_test_tick_clock_ptr =
+      simple_test_tick_clock.get();
+  service->SetTickClockForTesting(std::move(simple_test_tick_clock));
+
+  // Test that the preference is correctly initialized with the default value 0.
+  EXPECT_EQ(
+      0, pref_service()->GetInt64(prefs::kLastSuccessfulBackgroundFetchTime));
+
+  WaitForSnippetsServiceInitialization(service.get(),

[tschumann, 2016/12/08 18:18:51]

can you add a comment explaining that a fetch request was already triggered (by
which method? I guess MakeSnippetsServiceWithoutInitialization) but queued in
the event-loop. So we're only going to see the effect after this function.

+                                       /*set_empty_response=*/true);
+  EXPECT_EQ(
+      simple_test_tick_clock_ptr->NowTicks().ToInternalValue(),

[tschumann, 2016/12/08 18:18:51]

can you set up the clock's current time when initializing? How do I know it's
not initialized to zero and this just works accidentally?

+      pref_service()->GetInt64(prefs::kLastSuccessfulBackgroundFetchTime));
+
+  // Advance the time and check whether the time was updated correctly after the
+  // background fetch.
+  simple_test_tick_clock_ptr->Advance(TimeDelta::FromHours(1));
+  service->FetchSnippetsInTheBackground();
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(
+      simple_test_tick_clock_ptr->NowTicks().ToInternalValue(),
+      pref_service()->GetInt64(prefs::kLastSuccessfulBackgroundFetchTime));
+  // TODO(markusheintz): Add a test that simulates a browser restart once the
+  // scheduler refactoring is done (crbug.com/672434).
+}
+
 }  // namespace ntp_snippets