[Background Fetch] Add e2e browsertests for the full lifetime of a fetch

Change-Id: I172418ee124e867393cfb4a207fe4d898a06ec31
Reviewed-on: https://chromium-review.googlesource.com/1136447
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575274}

chrome/browser/background_fetch/background_fetch_browsertest.cc

@@ -88,7 +88,7 @@ class WaitableDownloadLoggerObserver : public download::Logger::Observer {
     const std::string& result = service_request.FindKey("result")->GetString();
 
     if (client != kBackgroundFetchClient)
-      return;  // this event is not targeted to us
+      return;  // This event is not targeted to us.
 
     if (result == kResultAccepted && download_accepted_callback_)
       std::move(download_accepted_callback_).Run(guid);
@@ -217,6 +217,15 @@ class BackgroundFetchBrowserTest : public InProcessBrowserTest {
     run_loop.Run();
   }
 
+  // Runs the |script| and waits for a background fetch event.
+  // Wrap in ASSERT_NO_FATAL_FAILURE().
+  void RunScriptAndCheckResultingEvent(const std::string& script,
+                                       const std::string& expected_event) {
+    std::string result;
+    ASSERT_NO_FATAL_FAILURE(RunScript(script, &result));
+    ASSERT_EQ(expected_event, result);
+  }
+
   void GetVisualsForOfflineItemSync(
       const ContentId& offline_item_id,
       std::unique_ptr<OfflineItemVisuals>* out_visuals) {
@@ -475,4 +484,12 @@ IN_PROC_BROWSER_TEST_F(
   EXPECT_EQ(offline_item.progress.unit, OfflineItemProgressUnit::PERCENTAGE);
 }
 
+IN_PROC_BROWSER_TEST_F(BackgroundFetchBrowserTest, FetchesRunToCompletion) {
+  // Starts two seperate multifile fetches and waits for them to complete.
+  ASSERT_NO_FATAL_FAILURE(RunScriptAndCheckResultingEvent(
+      "RunFetchTillCompletion()", "backgroundfetched"));
+  ASSERT_NO_FATAL_FAILURE(RunScriptAndCheckResultingEvent(
+      "RunFetchTillCompletionWithMissingResource()", "backgroundfetchfail"));
+}
+
 }  // namespace

chrome/test/data/background_fetch/background_fetch.js

@@ -84,3 +84,35 @@ function StartSingleFileDownloadWithCorrectDownloadTotal() {
     sendResultToTest('ok');
   }).catch(sendErrorToTest);
 }
+
+// Listens for a postMessage from sw.js and sends the result to the test.
+navigator.serviceWorker.addEventListener('message', (event) => {
+  if (['backgroundfetched', 'backgroundfetchfail'].includes(event.data))
+    sendResultToTest(event.data);
+  else
+    sendErrorToTest(Error('Unexpected message received: ' + event.data));
+});
+
+// Starts a Backgound Fetch that should succeed.
+function RunFetchTillCompletion() {
+  const resources = [
+    '/background_fetch/types_of_cheese.txt?idx=1',
+    '/background_fetch/types_of_cheese.txt?idx=2',
+  ];
+  navigator.serviceWorker.ready.then(swRegistration => {
+    return swRegistration.backgroundFetch.fetch(
+        kBackgroundFetchId, resources);
+  }).catch(sendErrorToTest);
+}
+
+// Starts a Background Fetch that should fail due to a missing resource.
+function RunFetchTillCompletionWithMissingResource() {
+  const resources = [
+    '/background_fetch/types_of_cheese.txt',
+    '/background_fetch/missing_cat.txt',
+  ];
+  navigator.serviceWorker.ready.then(swRegistration => {
+    return swRegistration.backgroundFetch.fetch(
+        kBackgroundFetchId, resources);
+  }).catch(sendErrorToTest);
+}

chrome/test/data/background_fetch/sw.js

@@ -2,4 +2,17 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Deliberately left empty.
+// Service Worker initialization listeners.
+self.addEventListener('install', e => e.waitUntil(skipWaiting()));
+self.addEventListener('activate', e => e.waitUntil(clients.claim()));
+
+// Posts |msg| to background_fetch.js.
+function postToWindowClients(msg) {
+  clients.matchAll({ type: 'window' }).then(clientWindows => {
+    for (const client of clientWindows) client.postMessage(msg);
+  });
+}
+
+// Background Fetch event listeners.
+self.addEventListener('backgroundfetched', e => postToWindowClients(e.type));
+self.addEventListener('backgroundfetchfail', e => postToWindowClients(e.type));
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