[Offline pages] Introduces TaskQueue to serialize tasks that asynchronously access SQLStore

components/offline_pages/core/task_queue_unittest.cc

+// 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/offline_pages/core/task_queue.h"
+
+#include <memory>
+
+#include "base/bind.h"
+#include "base/test/test_simple_task_runner.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "components/offline_pages/core/test_task.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace offline_pages {
+
+using TaskState = TestTask::TaskState;
+
+class OfflineTaskQueueTest : public testing::Test {
+ public:
+  OfflineTaskQueueTest();
+
+  void TaskCompleted(Task* task);
+  void PumpLoop();
+
+  Task* completed_task() const { return completed_task_; }
+
+ private:
+  Task* completed_task_;
+  scoped_refptr<base::TestSimpleTaskRunner> task_runner_;
+  base::ThreadTaskRunnerHandle task_runner_handle_;
+};
+
+OfflineTaskQueueTest::OfflineTaskQueueTest()
+    : completed_task_(nullptr),
+      task_runner_(new base::TestSimpleTaskRunner),
+      task_runner_handle_(task_runner_) {}
+
+void OfflineTaskQueueTest::PumpLoop() {
+  task_runner_->RunUntilIdle();
+}
+
+void OfflineTaskQueueTest::TaskCompleted(Task* task) {
+  completed_task_ = task;
+}
+
+TEST_F(OfflineTaskQueueTest, AddAndRunSingleTask) {
+  ConsumedResource resource;
+  std::unique_ptr<TestTask> task(new TestTask(&resource));
+  TestTask* task_ptr = task.get();
+  TaskQueue queue;
+  EXPECT_EQ(TaskState::NOT_STARTED, task_ptr->state());
+  queue.AddTask(std::move(task));
+  EXPECT_TRUE(queue.HasTasks());
+  EXPECT_TRUE(queue.CurrentlyRunning());
+  EXPECT_EQ(TaskState::STEP_1, task_ptr->state());
+  EXPECT_TRUE(resource.HasNextStep());
+  resource.CompleteStep();
+
+  EXPECT_EQ(TaskState::STEP_2, task_ptr->state());
+  EXPECT_TRUE(resource.HasNextStep());
+  resource.CompleteStep();
+
+  EXPECT_EQ(TaskState::COMPLETED, task_ptr->state());
+  EXPECT_FALSE(resource.HasNextStep());
+  PumpLoop();  // Deletes task, task_ptr is invalid after that.
+
+  EXPECT_FALSE(queue.CurrentlyRunning());
+  EXPECT_FALSE(queue.HasTasks());
+}
+
+TEST_F(OfflineTaskQueueTest, AddAndRunMultipleTasks) {
+  ConsumedResource resource;

[Pete Williamson, 2016/09/29 00:54:44]

Would it be safer to have different resources for each task?  (Maybe more
robust)

[fgorski, 2016/09/29 17:37:37]

No, why? The point is that tasks share the resource.

+  std::unique_ptr<TestTask> task_1(new TestTask(&resource));
+  TestTask* task_1_ptr = task_1.get();
+  std::unique_ptr<TestTask> task_2(new TestTask(&resource));
+  TestTask* task_2_ptr = task_2.get();
+
+  TaskQueue queue;
+  EXPECT_EQ(TaskState::NOT_STARTED, task_1_ptr->state());
+  EXPECT_EQ(TaskState::NOT_STARTED, task_2_ptr->state());
+  queue.AddTask(std::move(task_1));
+  queue.AddTask(std::move(task_2));
+  EXPECT_TRUE(queue.HasTasks());
+  EXPECT_TRUE(queue.CurrentlyRunning());
+  EXPECT_EQ(TaskState::STEP_1, task_1_ptr->state());
+  EXPECT_EQ(TaskState::NOT_STARTED, task_2_ptr->state());
+  resource.CompleteStep();
+
+  EXPECT_EQ(TaskState::STEP_2, task_1_ptr->state());
+  EXPECT_EQ(TaskState::NOT_STARTED, task_2_ptr->state());
+  resource.CompleteStep();
+
+  EXPECT_EQ(TaskState::COMPLETED, task_1_ptr->state());
+  EXPECT_EQ(TaskState::NOT_STARTED, task_2_ptr->state());
+  PumpLoop();  // Deletes task_1, task_1_ptr is invalid after that.
+  EXPECT_EQ(TaskState::STEP_1, task_2_ptr->state());
+}
+
+TEST_F(OfflineTaskQueueTest, LeaveEearly) {

[Pete Williamson, 2016/09/29 00:54:44]

nit -  LeaveEearly -> LeaveEarly

[fgorski, 2016/09/29 17:37:37]

Done.

+  ConsumedResource resource;
+  std::unique_ptr<TestTask> task(new TestTask(&resource, true));
+  TestTask* task_ptr = task.get();
+  TaskQueue queue;
+  EXPECT_EQ(TaskState::NOT_STARTED, task_ptr->state());
+  queue.AddTask(std::move(task));
+  EXPECT_TRUE(queue.HasTasks());
+  EXPECT_TRUE(queue.CurrentlyRunning());
+  EXPECT_EQ(TaskState::STEP_1, task_ptr->state());
+  EXPECT_TRUE(resource.HasNextStep());
+  resource.CompleteStep();

[Pete Williamson, 2016/09/29 00:54:44]

I don't see how this causes an early exit.  Comment, perhaps?

[fgorski, 2016/09/29 17:37:37]

Done.

+
+  EXPECT_EQ(TaskState::COMPLETED, task_ptr->state());
+  EXPECT_FALSE(resource.HasNextStep());
+  PumpLoop();  // Deletes task, task_ptr is invalid after that.
+
+  EXPECT_FALSE(queue.CurrentlyRunning());
+  EXPECT_FALSE(queue.HasTasks());
+}
+
+}  // namespace offline_pages