[NTP Snippets] Add unit tests for NTPSnippetsFetcher

components/ntp_snippets/ntp_snippets_fetcher_unittest.cc

Index: components/ntp_snippets/ntp_snippets_fetcher_unittest.cc
diff --git a/components/ntp_snippets/ntp_snippets_fetcher_unittest.cc b/components/ntp_snippets/ntp_snippets_fetcher_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..de1db09e624f9f52214f4999bb51576f384318ab
--- /dev/null
+++ b/components/ntp_snippets/ntp_snippets_fetcher_unittest.cc
@@ -0,0 +1,163 @@
+// 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/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::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:
+  MOCK_METHOD2(Run, void(const std::string& snippets_json,
+                         const std::string& status_message));
+};
+
+// Factory for FakeURLFetcher objects that always generate errors.
+class FailingFakeURLFetcherFactory : public net::URLFetcherFactory {
+ public:
+  std::unique_ptr<net::URLFetcher> CreateURLFetcher(
+      int id, const GURL& url, net::URLFetcher::RequestType request_type,
+      net::URLFetcherDelegate* d) override {
+    return base::WrapUnique(new net::FakeURLFetcher(
+        url, d, /*response_data=*/std::string(), net::HTTP_NOT_FOUND,
+        net::URLRequestStatus::FAILED));
+  }
+};
+
+class NTPSnippetsFetcherTest : public testing::Test {
+ public:
+  NTPSnippetsFetcherTest()
+      : fake_url_fetcher_factory_(
+            /*default_factory=*/&failing_url_fetcher_factory_),
+        snippets_fetcher_(scoped_refptr<base::SequencedTaskRunner>(),
+                          scoped_refptr<net::TestURLRequestContextGetter>(
+                              new net::TestURLRequestContextGetter(
+                                  base::ThreadTaskRunnerHandle::Get())),
+                          /*is_stable_channel=*/true),
+        test_url_(base::StringPrintf(kTestContentSnippetsServerFormat,
+                                     google_apis::GetAPIKey().c_str())) {
+    snippets_fetcher_subscription_ = snippets_fetcher_.AddCallback(
+        base::Bind(&MockSnippetsAvailableCallback::Run,
+                   base::Unretained(&mock_callback_)));
+  }
+
+  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_; }
+
+ 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_;
+
+  DISALLOW_COPY_AND_ASSIGN(NTPSnippetsFetcherTest);
+};
+
+TEST_F(NTPSnippetsFetcherTest, ShouldNotFetchOnCreation) {
+  // The lack of registered baked in responses would cause any fetch to fail.
+  RunUntilIdle();
+}
+
+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();
+}
+
+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();
+}
+
+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();
+}
+
+// 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();
+}
+
+}  // namespace
+}  // namespace ntp_snippets