Extract AD policy scheduler into separate class

components/policy/core/common/policy_scheduler_unittest.cc

+// Copyright 2017 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/policy/core/common/policy_scheduler.h"
+
+#include <memory>
+
+#include "base/memory/ptr_util.h"
+#include "base/memory/weak_ptr.h"
+#include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace policy {
+
+class PolicySchedulerTest : public testing::Test {
+ public:
+  void DoTask(PolicyScheduler::TaskCallback callback) {
+    do_counter_++;
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::BindOnce(std::move(callback), true));
+  }
+
+  void OnTaskDone(bool success) {
+    done_counter_++;
+
+    // Terminate PolicyScheduler after 5 iterations.
+    if (done_counter_ >= 5) {
+      base::ThreadTaskRunnerHandle::Get()->PostTask(
+          FROM_HERE, base::BindOnce(&PolicySchedulerTest::Terminate,
+                                    weak_ptr_factory_.GetWeakPtr()));
+    }
+  }
+
+  // To simulate a slow task the callback is captured instead of running it.
+  void CaptureCallbackForSlowTask(PolicyScheduler::TaskCallback callback) {
+    do_counter_++;
+    slow_callback_ = std::move(callback);
+  }
+
+  // Runs the captured callback to simulate the end of the slow task.
+  void PostSlowTaskCallback() {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::BindOnce(std::move(slow_callback_), true));
+  }
+
+  void Terminate() { scheduler_.reset(); }
+
+ protected:
+  int do_counter_ = 0;
+  int done_counter_ = 0;
+  std::unique_ptr<PolicyScheduler> scheduler_;
+
+  PolicyScheduler::TaskCallback slow_callback_;
+
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
+  base::WeakPtrFactory<PolicySchedulerTest> weak_ptr_factory_{this};

[pmarko, 2017/06/19 10:14:37]

Technically, WeakPtr is not necessary here because the test fixture instance
will always outlive the last task invocation in the tests, correct?

[Thiemo Nagel, 2017/06/19 22:29:51]

You're right.  Changed to base::Unretained().

+};
+
+TEST_F(PolicySchedulerTest, Run) {
+  scheduler_ = base::MakeUnique<PolicyScheduler>(
+      base::BindRepeating(&PolicySchedulerTest::DoTask,
+                          weak_ptr_factory_.GetWeakPtr()),
+      base::BindRepeating(&PolicySchedulerTest::OnTaskDone,
+                          weak_ptr_factory_.GetWeakPtr()),
+      base::TimeDelta::Max(), base::TimeDelta());

[pmarko, 2017/06/19 10:14:37]

Please consider adding /* interval */ and /* backoff_interval */ to these ctor
argument lists in the tests so the reader knows which is which without having to
look it up.

[Thiemo Nagel, 2017/06/19 22:29:51]

Good point.  Done.

+
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(1, done_counter_);
+}
+
+TEST_F(PolicySchedulerTest, Loop) {
+  scheduler_ = base::MakeUnique<PolicyScheduler>(
+      base::BindRepeating(&PolicySchedulerTest::DoTask,
+                          weak_ptr_factory_.GetWeakPtr()),
+      base::BindRepeating(&PolicySchedulerTest::OnTaskDone,
+                          weak_ptr_factory_.GetWeakPtr()),
+      base::TimeDelta(), base::TimeDelta());
+
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(5, done_counter_);
+}
+
+TEST_F(PolicySchedulerTest, Reschedule) {
+  scheduler_ = base::MakeUnique<PolicyScheduler>(
+      base::BindRepeating(&PolicySchedulerTest::DoTask,
+                          weak_ptr_factory_.GetWeakPtr()),
+      base::BindRepeating(&PolicySchedulerTest::OnTaskDone,
+                          weak_ptr_factory_.GetWeakPtr()),
+      base::TimeDelta::Max(), base::TimeDelta());
+
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(1, done_counter_);
+
+  // Delayed action is not run.
+  scheduler_->ScheduleTask(base::TimeDelta::Max());
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(1, done_counter_);
+
+  // Rescheduling with 0 delay causes it to run.
+  scheduler_->ScheduleTask(base::TimeDelta());
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(2, done_counter_);
+}
+
+TEST_F(PolicySchedulerTest, OverlappingTasks) {
+  scheduler_ = base::MakeUnique<PolicyScheduler>(
+      base::BindRepeating(&PolicySchedulerTest::CaptureCallbackForSlowTask,
+                          weak_ptr_factory_.GetWeakPtr()),
+      base::BindRepeating(&PolicySchedulerTest::OnTaskDone,
+                          weak_ptr_factory_.GetWeakPtr()),
+      base::TimeDelta::Max(), base::TimeDelta());
+
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(1, do_counter_);
+  EXPECT_EQ(0, done_counter_);
+
+  // Second action doesn't start while first is still pending.
+  scheduler_->ScheduleTask(base::TimeDelta());
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(1, do_counter_);
+  EXPECT_EQ(0, done_counter_);
+
+  // After first action has finished, the second is started.
+  PostSlowTaskCallback();
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(2, do_counter_);
+  EXPECT_EQ(1, done_counter_);
+
+  // Let the second action finish.
+  PostSlowTaskCallback();
+  base::RunLoop().RunUntilIdle();
+  EXPECT_EQ(2, do_counter_);
+  EXPECT_EQ(2, done_counter_);
+}
+
+}  // namespace policy