FetchMore functionality backend

components/ntp_snippets/remote/ntp_snippets_service_unittest.cc

Index: components/ntp_snippets/remote/ntp_snippets_service_unittest.cc
diff --git a/components/ntp_snippets/remote/ntp_snippets_service_unittest.cc b/components/ntp_snippets/remote/ntp_snippets_service_unittest.cc
index e79d79ca5cb4aa48b17018157061004d7ca987ea..b35abf1d935a6e2546f60efc6f8f6f24be43647c 100644
--- a/components/ntp_snippets/remote/ntp_snippets_service_unittest.cc
+++ b/components/ntp_snippets/remote/ntp_snippets_service_unittest.cc
@@ -388,7 +388,8 @@ class NTPSnippetsServiceTest : public ::testing::Test {
         test_url_(kTestContentSuggestionsServerWithAPIKey),
         user_classifier_(/*pref_service=*/nullptr),
         image_fetcher_(nullptr),
-        image_decoder_(nullptr) {
+        image_decoder_(nullptr),
+        caller_() {
     NTPSnippetsService::RegisterProfilePrefs(utils_.pref_service()->registry());
     RequestThrottler::RegisterProfilePrefs(utils_.pref_service()->registry());
 
@@ -503,7 +504,34 @@ class NTPSnippetsServiceTest : public ::testing::Test {
     base::RunLoop().RunUntilIdle();
   }
 
+  void LoadMoreFromJSONString(
+      NTPSnippetsService* service,
+      const std::string& json,
+      NTPSnippetsService::FetchedMoreCallback callback) {
+    SetUpFetchResponse(json);
+    service->FetchMore(articles_category(), callback);
+    base::RunLoop().RunUntilIdle();
+  }
+
+  NTPSnippetsService::FetchedMoreCallback MakeDummyCallback() {
+    return base::Bind(&MockCaller::EmptyCallback,
+                      base::Unretained(&this->caller_));
+  }
+
+  NTPSnippetsService::FetchedMoreCallback MakeMustCallCallback() {
+    EXPECT_CALL(this->caller_, MustCallback()).Times(1);
+    return base::Bind(&MockCaller::CheckCallback,
+                      base::Unretained(&this->caller_));
+  }
+
  private:
+  class MockCaller {
+   public:
+    void EmptyCallback(std::vector<ContentSuggestion>) {}
+    void CheckCallback(std::vector<ContentSuggestion> v) { MustCallback(); }
+    MOCK_METHOD0(MustCallback, void());

[Marc Treib, 2016/10/20 16:51:40]

No need for a class - you can use a MockFunction for the mock method, and
probably just base::Bind an empty lambda for the non-checked one.

[Marc Treib, 2016/10/28 14:49:50]

Done.

+  };
+
   variations::testing::VariationParamsManager params_manager_;
   test::NTPSnippetsTestUtils utils_;
   base::MessageLoop message_loop_;
@@ -520,6 +548,7 @@ class NTPSnippetsServiceTest : public ::testing::Test {
   FakeImageDecoder* image_decoder_;
 
   base::ScopedTempDir database_dir_;
+  MockCaller caller_;
 
   DISALLOW_COPY_AND_ASSIGN(NTPSnippetsServiceTest);
 };
@@ -832,6 +861,33 @@ TEST_F(NTPSnippetsServiceTest, ReplaceSnippets) {
               ElementsAre(IdEq(second)));
 }
 
+TEST_F(NTPSnippetsServiceTest, LoadsAdditionalSnippets) {
+  auto service = MakeSnippetsService();
+
+  std::string first("http://first");
+  LoadFromJSONString(service.get(), GetTestJson({GetSnippetWithUrl(first)}));
+  EXPECT_THAT(service->GetSnippetsForTesting(articles_category()),
+              ElementsAre(IdEq(first)));
+
+  std::string second("http://second");
+  LoadMoreFromJSONString(service.get(),
+                         GetTestJson({GetSnippetWithUrl(second)}),
+                         MakeDummyCallback());
+  // The snippets loaded last are added to the previously loaded.
+  EXPECT_THAT(service->GetSnippetsForTesting(articles_category()),
+              ElementsAre(IdEq(first), IdEq(second)));
+}
+
+TEST_F(NTPSnippetsServiceTest, InvokesOnlyCallbackOnFetchingMore) {
+  LoadMoreFromJSONString(MakeSnippetsService().get(),

[Marc Treib, 2016/10/20 16:51:40]

Hm, like this, the SnippetsService gets destroyed immediately after
LoadMoreFromJSONString finished. Could that cause any trouble?

[Marc Treib, 2016/10/28 14:49:50]

Done.

+                         GetTestJson({GetSnippetWithUrl("http://some")}),
+                         MakeMustCallCallback());
+
+  // The observer shouldn't have been triggered.
+  EXPECT_THAT(observer().SuggestionsForCategory(articles_category()),
+              SizeIs(0));

[Marc Treib, 2016/10/20 16:51:40]

You can also do
EXPECT_CALL(...).Times(0)
to make sure it really isn't called.

[Marc Treib, 2016/10/28 14:49:50]

...except that you can't, because the observer isn't a mock :)

+}
+
 TEST_F(NTPSnippetsServiceTest, LoadInvalidJson) {
   auto service = MakeSnippetsService();