[NTP Snippets] Add newly-fetched snippets at the front instead of at the end

components/ntp_snippets/ntp_snippets_service_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/ntp_snippets_service.h"
 
 #include "base/json/json_reader.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 172 matching lines @@
   // CreateSnippetsServiceEnabled checks that Schedule is called.
 }
 
 TEST_F(NTPSnippetsServiceDisabledTest, Unschedule) {
   // CreateSnippetsServiceEnabled checks that Unschedule is called.
 }
 
 TEST_F(NTPSnippetsServiceTest, Loop) {
   std::string json_str(
       "{ \"recos\": [ "
-      "{ \"contentInfo\": { \"url\" : \"http://localhost/foobar\" }}"
+      "  { \"contentInfo\": { \"url\" : \"http://localhost/foobar\" }}"
       "]}");
   LoadFromJSONString(json_str);
 
   // The same for loop without the '&' should not compile.
   for (auto& snippet : *service()) {
     // Snippet here is a const.
     EXPECT_EQ(snippet.url(), GURL("http://localhost/foobar"));
   }
   // Without the const, this should not compile.
   for (const NTPSnippet& snippet : *service()) {
@@ skipping 25 matching lines @@
 TEST_F(NTPSnippetsServiceTest, Clear) {
   std::string json_str(GetTestJson());
 
   LoadFromJSONString(json_str);
   EXPECT_EQ(service()->size(), 1u);
 
   service()->ClearSnippets();
   EXPECT_EQ(service()->size(), 0u);
 }
 
+TEST_F(NTPSnippetsServiceTest, InsertAtFront) {
+  std::string json_str(
+      "{ \"recos\": [ "
+      "  { \"contentInfo\": { \"url\" : \"http://first\" }}"
+      "]}");
+  LoadFromJSONString(json_str);
+  ASSERT_EQ(service()->size(), 1u);
+
+  std::string json_str2(
+      "{ \"recos\": [ "
+      "  { \"contentInfo\": { \"url\" : \"http://second\" }}"
+      "]}");
+  LoadFromJSONString(json_str2);
+  ASSERT_EQ(service()->size(), 2u);
+
+  // The snippet loaded last should be at the first position in the list now.
+  const NTPSnippet& first_snippet = *service()->begin();
+  EXPECT_EQ(first_snippet.url(), GURL("http://second"));
+}
+
 TEST_F(NTPSnippetsServiceTest, LoadInvalidJson) {
   SetExpectJsonParseSuccess(false);
   LoadFromJSONString(GetInvalidJson());
   EXPECT_EQ(service()->size(), 0u);
 }
 
 TEST_F(NTPSnippetsServiceTest, LoadInvalidJsonWithExistingSnippets) {
   LoadFromJSONString(GetTestJson());
   ASSERT_EQ(service()->size(), 1u);
 
@@ skipping 84 matching lines @@
 }
 
 TEST_F(NTPSnippetsServiceTest, RemoveExpiredContent) {
   std::string json_str(GetTestExpiredJson());
 
   LoadFromJSONString(json_str);
   EXPECT_EQ(service()->size(), 0u);
 }
 
 }  // namespace ntp_snippets