[NTP Snippets] FetchMore 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..c69d7ebaaf2ce3b19a9ea7310bda0314f7bdd70b 100644
--- a/components/ntp_snippets/remote/ntp_snippets_service_unittest.cc
+++ b/components/ntp_snippets/remote/ntp_snippets_service_unittest.cc
@@ -503,6 +503,15 @@ 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();
+  }
+
  private:
   variations::testing::VariationParamsManager params_manager_;
   test::NTPSnippetsTestUtils utils_;
@@ -832,6 +841,49 @@ 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)}),
+                         base::Bind([](std::vector<ContentSuggestion>) {}));
+  // The snippets loaded last are added to the previously loaded.
+  EXPECT_THAT(service->GetSnippetsForTesting(articles_category()),
+              ElementsAre(IdEq(first), IdEq(second)));
+}
+
+namespace {
+
+// Workaround for gMock's lack of support for movable types.
+void SuggestionsLoaded(
+    MockFunction<void(const std::vector<ContentSuggestion>& v)>* loaded,
+    std::vector<ContentSuggestion> v) {
+  loaded->Call(v);
+}
+
+}  // namespace
+
+TEST_F(NTPSnippetsServiceTest, InvokesOnlyCallbackOnFetchingMore) {
+  auto service = MakeSnippetsService();
+
+  MockFunction<void(const std::vector<ContentSuggestion>&)> loaded;
+  EXPECT_CALL(loaded, Call(SizeIs(1)));
+
+  LoadMoreFromJSONString(service.get(),
+                         GetTestJson({GetSnippetWithUrl("http://some")}),
+                         base::Bind(&SuggestionsLoaded, &loaded));
+
+  // The observer shouldn't have been triggered.
+  EXPECT_THAT(observer().SuggestionsForCategory(articles_category()),
+              IsEmpty());
+}
+
 TEST_F(NTPSnippetsServiceTest, LoadInvalidJson) {
   auto service = MakeSnippetsService();