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

components/offline_pages/core/task_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.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 OfflineTaskTest : public testing::Test {
+ public:
+  OfflineTaskTest();
+
+  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_;
+};
+
+OfflineTaskTest::OfflineTaskTest()
+    : completed_task_(nullptr),
+      task_runner_(new base::TestSimpleTaskRunner),
+      task_runner_handle_(task_runner_) {}
+
+void OfflineTaskTest::PumpLoop() {
+  task_runner_->RunUntilIdle();
+}
+
+void OfflineTaskTest::TaskCompleted(Task* task) {
+  completed_task_ = task;
+}
+
+TEST_F(OfflineTaskTest, RunTaskStepByStep) {
+  ConsumedResource resource;
+  TestTask task(&resource);
+  task.SetTaskCompletionCallbackForTesting(
+      base::ThreadTaskRunnerHandle::Get(),
+      base::Bind(&OfflineTaskTest::TaskCompleted, base::Unretained(this)));
+
+  EXPECT_EQ(TaskState::NOT_STARTED, task.state());
+  task.Run();
+  EXPECT_EQ(TaskState::STEP_1, task.state());
+  EXPECT_TRUE(resource.HasNextStep());
+  resource.CompleteStep();
+  EXPECT_EQ(TaskState::STEP_2, task.state());
+  EXPECT_TRUE(resource.HasNextStep());
+  resource.CompleteStep();
+  EXPECT_EQ(TaskState::COMPLETED, task.state());
+  PumpLoop();
+  EXPECT_EQ(completed_task(), &task);
+}
+
+TEST_F(OfflineTaskTest, LeaveEarly) {
+  ConsumedResource resource;
+  TestTask task(&resource, true /* leave early */);
+  EXPECT_EQ(TaskState::NOT_STARTED, task.state());
+  task.Run();
+  EXPECT_EQ(TaskState::STEP_1, task.state());
+  EXPECT_TRUE(resource.HasNextStep());
+  resource.CompleteStep();
+
+  // Notice STEP_2 was omitted and task went from STEP_1 to completed.
+  EXPECT_EQ(TaskState::COMPLETED, task.state());
+  EXPECT_FALSE(resource.HasNextStep());
+}
+
+}  // namespace offline_pages