Add TimeController to api/test/ and add a CreateTimeController API.

Creates an abstraction for an "alarm clock" which can schedule
time-controller callbacks and exposes a time controller driven by
an external alarm.

Bug: webrtc:9719
Change-Id: I08c2aa9dba25603043bfba48f55c925716a55bae
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/158969
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Reviewed-by: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Bjorn Mellem <mellem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29879}

api/BUILD.gn

@@ -946,6 +946,45 @@ if (rtc_include_tests) {
     ]
   }
 
+  rtc_library("time_controller") {
+    visibility = [ "*" ]
+    testonly = true
+    sources = [
+      "test/time_controller.h",
+    ]
+
+    deps = [
+      "../modules:module_api",
+      "../modules/utility:utility",
+      "../rtc_base",
+      "../rtc_base:rtc_base_tests_utils",
+      "../rtc_base:rtc_event",
+      "../rtc_base/synchronization:sequence_checker",
+      "../rtc_base/synchronization:yield_policy",
+      "../rtc_base/task_utils:to_queued_task",
+      "../system_wrappers",
+      "task_queue",
+      "task_queue:default_task_queue_factory",
+      "units:time_delta",
+      "units:timestamp",
+      "//third_party/abseil-cpp/absl/strings",
+    ]
+  }
+
+  rtc_library("create_time_controller") {
+    visibility = [ "*" ]
+    testonly = true
+    sources = [
+      "test/create_time_controller.cc",
+      "test/create_time_controller.h",
+    ]
+
+    deps = [
+      ":time_controller",
+      "../test/time_controller",
+    ]
+  }
+
   rtc_library("rtc_api_unittests") {
     testonly = true
 
@@ -958,11 +997,13 @@ if (rtc_include_tests) {
       "rtp_packet_infos_unittest.cc",
       "rtp_parameters_unittest.cc",
       "scoped_refptr_unittest.cc",
+      "test/create_time_controller_unittest.cc",
       "test/loopback_media_transport_unittest.cc",
     ]
 
     deps = [
       ":array_view",
+      ":create_time_controller",
       ":function_view",
       ":libjingle_peerconnection_api",
       ":loopback_media_transport",
@@ -971,12 +1012,17 @@ if (rtc_include_tests) {
       ":rtp_packet_info",
       ":rtp_parameters",
       ":scoped_refptr",
+      ":time_controller",
       "../rtc_base:checks",
       "../rtc_base:gunit_helpers",
       "../rtc_base:rtc_base_approved",
+      "../rtc_base:rtc_task_queue",
+      "../rtc_base/task_utils:repeating_task",
       "../test:fileutils",
       "../test:test_support",
       "task_queue:task_queue_default_factory_unittests",
+      "units:time_delta",
+      "units:timestamp",
       "units:units_unittests",
       "video:video_unittests",
     ]

api/test/DEPS

@@ -32,4 +32,9 @@ specific_include_rules = {
     "+rtc_base/thread.h",
     "+media/base/media_constants.h",
   ],
+  "time_controller\.h": [
+    "+modules/utility/include/process_thread.h",
+    "+rtc_base/synchronization/yield_policy.h",
+    "+system_wrappers/include/clock.h",
+  ],
 }

api/test/create_time_controller.cc

@@ -0,0 +1,24 @@
+/*
+ *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "api/test/create_time_controller.h"
+
+#include <memory>
+
+#include "test/time_controller/external_time_controller.h"
+
+namespace webrtc {
+
+std::unique_ptr<TimeController> CreateTimeController(
+    ControlledAlarmClock* alarm) {
+  return std::make_unique<ExternalTimeController>(alarm);
+}
+
+}  // namespace webrtc

api/test/create_time_controller.h

@@ -0,0 +1,24 @@
+/*
+ *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#ifndef API_TEST_CREATE_TIME_CONTROLLER_H_
+#define API_TEST_CREATE_TIME_CONTROLLER_H_
+
+#include <memory>
+
+#include "api/test/time_controller.h"
+
+namespace webrtc {
+
+std::unique_ptr<TimeController> CreateTimeController(
+    ControlledAlarmClock* alarm);
+
+}  // namespace webrtc
+
+#endif  // API_TEST_CREATE_TIME_CONTROLLER_H_

api/test/create_time_controller_unittest.cc

@@ -0,0 +1,76 @@
+/*
+ *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "api/test/create_time_controller.h"
+
+#include "api/test/time_controller.h"
+#include "api/units/time_delta.h"
+#include "api/units/timestamp.h"
+#include "test/gmock.h"
+#include "test/gtest.h"
+
+namespace webrtc {
+namespace {
+
+class FakeAlarm : public ControlledAlarmClock {
+ public:
+  explicit FakeAlarm(Timestamp start_time);
+
+  Clock* GetClock() override;
+  bool ScheduleAlarmAt(Timestamp deadline) override;
+  void SetCallback(std::function<void()> callback) override;
+  void Sleep(TimeDelta duration) override;
+
+ private:
+  SimulatedClock clock_;
+  Timestamp deadline_;
+  std::function<void()> callback_;
+};
+
+FakeAlarm::FakeAlarm(Timestamp start_time)
+    : clock_(start_time),
+      deadline_(Timestamp::PlusInfinity()),
+      callback_([] {}) {}
+
+Clock* FakeAlarm::GetClock() {
+  return &clock_;
+}
+
+bool FakeAlarm::ScheduleAlarmAt(Timestamp deadline) {
+  if (deadline < deadline_) {
+    deadline_ = deadline;
+    return true;
+  }
+  return false;
+}
+
+void FakeAlarm::SetCallback(std::function<void()> callback) {
+  callback_ = callback;
+}
+
+void FakeAlarm::Sleep(TimeDelta duration) {
+  Timestamp end_time = clock_.CurrentTime() + duration;
+
+  while (deadline_ <= end_time) {
+    clock_.AdvanceTime(deadline_ - clock_.CurrentTime());
+    deadline_ = Timestamp::PlusInfinity();
+    callback_();
+  }
+
+  clock_.AdvanceTime(end_time - clock_.CurrentTime());
+}
+
+TEST(CreateTimeControllerTest, CreatesNonNullController) {
+  FakeAlarm alarm(Timestamp::ms(100));
+  EXPECT_NE(CreateTimeController(&alarm), nullptr);
+}
+
+}  // namespace
+}  // namespace webrtc

api/test/time_controller.h

@@ -7,15 +7,17 @@
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
-#ifndef TEST_TIME_CONTROLLER_TIME_CONTROLLER_H_
+#ifndef API_TEST_TIME_CONTROLLER_H_
-#define TEST_TIME_CONTROLLER_TIME_CONTROLLER_H_
+#define API_TEST_TIME_CONTROLLER_H_
 
 #include <functional>
 #include <memory>
 
 #include "api/task_queue/task_queue_factory.h"
 #include "api/units/time_delta.h"
+#include "api/units/timestamp.h"
 #include "modules/utility/include/process_thread.h"
+#include "rtc_base/synchronization/yield_policy.h"
 #include "system_wrappers/include/clock.h"
 
 namespace webrtc {
@@ -42,6 +44,32 @@ class TimeController {
   // might yield to execute other tasks. This allows doing blocking waits on
   // tasks on other task queues froma a task queue without deadlocking.
   virtual void InvokeWithControlledYield(std::function<void()> closure) = 0;
+  // Returns a YieldInterface which can be installed as a ScopedYieldPolicy.
+  virtual rtc::YieldInterface* YieldInterface() = 0;
 };
+
+// Interface for telling time, scheduling an event to fire at a particular time,
+// and waiting for time to pass.
+class ControlledAlarmClock {
+ public:
+  virtual ~ControlledAlarmClock() = default;
+
+  // Gets a clock that tells the alarm clock's notion of time.
+  virtual Clock* GetClock() = 0;
+
+  // Schedules the alarm to fire at |deadline|.
+  // An alarm clock only supports one deadline. Calls to |ScheduleAlarmAt| with
+  // an earlier deadline will reset the alarm to fire earlier.Calls to
+  // |ScheduleAlarmAt| with a later deadline are ignored. Returns true if the
+  // deadline changed, false otherwise.
+  virtual bool ScheduleAlarmAt(Timestamp deadline) = 0;
+
+  // Sets the callback that should be run when the alarm fires.
+  virtual void SetCallback(std::function<void()> callback) = 0;
+
+  // Waits for |duration| to pass, according to the alarm clock.
+  virtual void Sleep(TimeDelta duration) = 0;
+};
+
 }  // namespace webrtc
-#endif  // TEST_TIME_CONTROLLER_TIME_CONTROLLER_H_
+#endif  // API_TEST_TIME_CONTROLLER_H_

test/network/BUILD.gn

@@ -41,6 +41,7 @@ rtc_library("emulated_network") {
   deps = [
     "../../api:network_emulation_manager_api",
     "../../api:simulated_network_api",
+    "../../api:time_controller",
     "../../api/units:data_rate",
     "../../api/units:data_size",
     "../../api/units:time_delta",

test/network/network_emulation_manager.h

@@ -19,6 +19,7 @@
 
 #include "api/test/network_emulation_manager.h"
 #include "api/test/simulated_network.h"
+#include "api/test/time_controller.h"
 #include "api/units/time_delta.h"
 #include "api/units/timestamp.h"
 #include "rtc_base/logging.h"
@@ -33,7 +34,6 @@
 #include "test/network/network_emulation.h"
 #include "test/network/simulated_network_node.h"
 #include "test/network/traffic_route.h"
-#include "test/time_controller/time_controller.h"
 
 namespace webrtc {
 namespace test {

test/scenario/BUILD.gn

@@ -84,6 +84,8 @@ if (rtc_include_tests) {
       "../../api:libjingle_peerconnection_api",
       "../../api:rtc_event_log_output_file",
       "../../api:rtp_parameters",
+      "../../api:time_controller",
+      "../../api:time_controller",
       "../../api:transport_api",
       "../../api/audio_codecs:builtin_audio_decoder_factory",
       "../../api/audio_codecs:builtin_audio_encoder_factory",

test/scenario/call_client.h

@@ -17,6 +17,7 @@
 #include <vector>
 
 #include "api/rtc_event_log/rtc_event_log.h"
+#include "api/test/time_controller.h"
 #include "call/call.h"
 #include "modules/audio_device/include/test_audio_device.h"
 #include "modules/congestion_controller/goog_cc/test/goog_cc_printer.h"
@@ -28,7 +29,6 @@
 #include "test/scenario/column_printer.h"
 #include "test/scenario/network_node.h"
 #include "test/scenario/scenario_config.h"
-#include "test/time_controller/time_controller.h"
 
 namespace webrtc {
 

test/scenario/scenario.h

@@ -14,6 +14,7 @@
 #include <utility>
 #include <vector>
 
+#include "api/test/time_controller.h"
 #include "rtc_base/constructor_magic.h"
 #include "rtc_base/fake_clock.h"
 #include "rtc_base/task_queue.h"
@@ -26,7 +27,6 @@
 #include "test/scenario/network_node.h"
 #include "test/scenario/scenario_config.h"
 #include "test/scenario/video_stream.h"
-#include "test/time_controller/time_controller.h"
 
 namespace webrtc {
 namespace test {

test/time_controller/BUILD.gn

@@ -12,14 +12,16 @@ if (rtc_include_tests) {
   rtc_library("time_controller") {
     testonly = true
     sources = [
+      "external_time_controller.cc",
+      "external_time_controller.h",
       "real_time_controller.cc",
       "real_time_controller.h",
       "simulated_time_controller.cc",
       "simulated_time_controller.h",
-      "time_controller.h",
     ]
 
     deps = [
+      "../../api:time_controller",
       "../../api/task_queue",
       "../../api/task_queue:default_task_queue_factory",
       "../../api/units:time_delta",
@@ -39,6 +41,7 @@ if (rtc_include_tests) {
   rtc_library("time_controller_unittests") {
     testonly = true
     sources = [
+      "external_time_controller_unittest.cc",
       "simulated_time_controller_unittest.cc",
     ]
     deps = [

test/time_controller/external_time_controller.cc

@@ -0,0 +1,226 @@
+/*
+ *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#include "test/time_controller/external_time_controller.h"
+
+#include <algorithm>
+#include <map>
+#include <memory>
+#include <utility>
+
+#include "api/task_queue/queued_task.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/task_queue/task_queue_factory.h"
+#include "api/units/time_delta.h"
+#include "api/units/timestamp.h"
+#include "modules/include/module.h"
+#include "modules/utility/include/process_thread.h"
+#include "rtc_base/synchronization/yield_policy.h"
+#include "test/time_controller/simulated_time_controller.h"
+
+namespace webrtc {
+
+// Wraps a ProcessThread so that it can reschedule the time controller whenever
+// an external call changes the ProcessThread's state.  For example, when a new
+// module is registered, the ProcessThread may need to be called sooner than the
+// time controller's currently-scheduled deadline.
+class ExternalTimeController::ProcessThreadWrapper : public ProcessThread {
+ public:
+  ProcessThreadWrapper(ExternalTimeController* parent,
+                       std::unique_ptr<ProcessThread> thread)
+      : parent_(parent), thread_(std::move(thread)) {}
+
+  void Start() override {
+    parent_->UpdateTime();
+    thread_->Start();
+    parent_->ScheduleNext();
+  }
+
+  void Stop() override {
+    parent_->UpdateTime();
+    thread_->Stop();
+    parent_->ScheduleNext();
+  }
+
+  void WakeUp(Module* module) override {
+    parent_->UpdateTime();
+    thread_->WakeUp(GetWrapper(module));
+    parent_->ScheduleNext();
+  }
+
+  void PostTask(std::unique_ptr<QueuedTask> task) override {
+    parent_->UpdateTime();
+    thread_->PostTask(std::move(task));
+    parent_->ScheduleNext();
+  }
+
+  void RegisterModule(Module* module, const rtc::Location& from) override {
+    parent_->UpdateTime();
+    module_wrappers_.emplace(module, new ModuleWrapper(module, this));
+    thread_->RegisterModule(GetWrapper(module), from);
+    parent_->ScheduleNext();
+  }
+
+  void DeRegisterModule(Module* module) override {
+    parent_->UpdateTime();
+    thread_->DeRegisterModule(GetWrapper(module));
+    parent_->ScheduleNext();
+    module_wrappers_.erase(module);
+  }
+
+ private:
+  class ModuleWrapper : public Module {
+   public:
+    ModuleWrapper(Module* module, ProcessThreadWrapper* thread)
+        : module_(module), thread_(thread) {}
+
+    int64_t TimeUntilNextProcess() override {
+      return module_->TimeUntilNextProcess();
+    }
+
+    void Process() override { module_->Process(); }
+
+    void ProcessThreadAttached(ProcessThread* process_thread) override {
+      if (process_thread) {
+        module_->ProcessThreadAttached(thread_);
+      } else {
+        module_->ProcessThreadAttached(nullptr);
+      }
+    }
+
+   private:
+    Module* module_;
+    ProcessThreadWrapper* thread_;
+  };
+
+  ModuleWrapper* GetWrapper(Module* module) {
+    auto it = module_wrappers_.find(module);
+    RTC_DCHECK(it != module_wrappers_.end());
+    return it->second.get();
+  }
+
+  ExternalTimeController* const parent_;
+  std::unique_ptr<ProcessThread> thread_;
+  std::map<Module*, std::unique_ptr<ModuleWrapper>> module_wrappers_;
+};
+
+// Wraps a TaskQueue so that it can reschedule the time controller whenever
+// an external call schedules a new task.
+class ExternalTimeController::TaskQueueWrapper : public TaskQueueBase {
+ public:
+  TaskQueueWrapper(ExternalTimeController* parent,
+                   std::unique_ptr<TaskQueueBase, TaskQueueDeleter> base)
+      : parent_(parent), base_(std::move(base)) {}
+
+  void PostTask(std::unique_ptr<QueuedTask> task) override {
+    parent_->UpdateTime();
+    base_->PostTask(std::make_unique<TaskWrapper>(std::move(task), this));
+    parent_->ScheduleNext();
+  }
+
+  void PostDelayedTask(std::unique_ptr<QueuedTask> task, uint32_t ms) override {
+    parent_->UpdateTime();
+    base_->PostDelayedTask(std::make_unique<TaskWrapper>(std::move(task), this),
+                           ms);
+    parent_->ScheduleNext();
+  }
+
+  void Delete() override { delete this; }
+
+ private:
+  class TaskWrapper : public QueuedTask {
+   public:
+    TaskWrapper(std::unique_ptr<QueuedTask> task, TaskQueueWrapper* queue)
+        : task_(std::move(task)), queue_(queue) {}
+
+    bool Run() override {
+      CurrentTaskQueueSetter current(queue_);
+      if (!task_->Run()) {
+        task_.release();
+      }
+      // The wrapper should always be deleted, even if it releases the inner
+      // task, in order to avoid leaking wrappers.
+      return true;
+    }
+
+   private:
+    std::unique_ptr<QueuedTask> task_;
+    TaskQueueWrapper* queue_;
+  };
+
+  ExternalTimeController* const parent_;
+  std::unique_ptr<TaskQueueBase, TaskQueueDeleter> base_;
+};
+
+ExternalTimeController::ExternalTimeController(ControlledAlarmClock* alarm)
+    : alarm_(alarm), impl_(alarm_->GetClock()->CurrentTime()) {
+  global_clock_.SetTime(alarm_->GetClock()->CurrentTime());
+  alarm_->SetCallback([this] { Run(); });
+}
+
+Clock* ExternalTimeController::GetClock() {
+  return alarm_->GetClock();
+}
+
+TaskQueueFactory* ExternalTimeController::GetTaskQueueFactory() {
+  return this;
+}
+
+std::unique_ptr<ProcessThread> ExternalTimeController::CreateProcessThread(
+    const char* thread_name) {
+  return std::make_unique<ProcessThreadWrapper>(
+      this, impl_.CreateProcessThread(thread_name));
+}
+
+void ExternalTimeController::Sleep(TimeDelta duration) {
+  alarm_->Sleep(duration);
+}
+
+void ExternalTimeController::InvokeWithControlledYield(
+    std::function<void()> closure) {
+  rtc::ScopedYieldPolicy policy(YieldInterface());
+  closure();
+}
+
+rtc::YieldInterface* ExternalTimeController::YieldInterface() {
+  return &impl_;
+}
+
+std::unique_ptr<TaskQueueBase, TaskQueueDeleter>
+ExternalTimeController::CreateTaskQueue(
+    absl::string_view name,
+    TaskQueueFactory::Priority priority) const {
+  return std::unique_ptr<TaskQueueBase, TaskQueueDeleter>(
+      new TaskQueueWrapper(const_cast<ExternalTimeController*>(this),
+                           impl_.CreateTaskQueue(name, priority)));
+}
+
+void ExternalTimeController::Run() {
+  rtc::ScopedYieldPolicy yield_policy(&impl_);
+  UpdateTime();
+  impl_.RunReadyRunners();
+  ScheduleNext();
+}
+
+void ExternalTimeController::UpdateTime() {
+  Timestamp now = alarm_->GetClock()->CurrentTime();
+  impl_.AdvanceTime(now);
+  global_clock_.SetTime(now);
+}
+
+void ExternalTimeController::ScheduleNext() {
+  RTC_DCHECK_EQ(impl_.CurrentTime(), alarm_->GetClock()->CurrentTime());
+  TimeDelta delay =
+      std::max(impl_.NextRunTime() - impl_.CurrentTime(), TimeDelta::Zero());
+  if (delay.IsFinite()) {
+    alarm_->ScheduleAlarmAt(alarm_->GetClock()->CurrentTime() + delay);
+  }
+}
+
+}  // namespace webrtc

test/time_controller/external_time_controller.h

@@ -0,0 +1,70 @@
+/*
+ *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#ifndef TEST_TIME_CONTROLLER_EXTERNAL_TIME_CONTROLLER_H_
+#define TEST_TIME_CONTROLLER_EXTERNAL_TIME_CONTROLLER_H_
+
+#include <functional>
+#include <memory>
+
+#include "absl/strings/string_view.h"
+#include "api/task_queue/task_queue_base.h"
+#include "api/task_queue/task_queue_factory.h"
+#include "api/test/time_controller.h"
+#include "api/units/time_delta.h"
+#include "api/units/timestamp.h"
+#include "modules/utility/include/process_thread.h"
+#include "system_wrappers/include/clock.h"
+#include "test/time_controller/simulated_time_controller.h"
+
+namespace webrtc {
+
+// TimeController implementation built on an external controlled alarm.
+// This implementation is used to delegate scheduling and execution to an
+// external run loop.
+class ExternalTimeController : public TimeController, public TaskQueueFactory {
+ public:
+  explicit ExternalTimeController(ControlledAlarmClock* alarm);
+
+  // Implementation of TimeController.
+  Clock* GetClock() override;
+  TaskQueueFactory* GetTaskQueueFactory() override;
+  std::unique_ptr<ProcessThread> CreateProcessThread(
+      const char* thread_name) override;
+  void Sleep(TimeDelta duration) override;
+  void InvokeWithControlledYield(std::function<void()> closure) override;
+  rtc::YieldInterface* YieldInterface() override;
+
+  // Implementation of TaskQueueFactory.
+  std::unique_ptr<TaskQueueBase, TaskQueueDeleter> CreateTaskQueue(
+      absl::string_view name,
+      TaskQueueFactory::Priority priority) const override;
+
+ private:
+  class ProcessThreadWrapper;
+  class TaskQueueWrapper;
+
+  // Executes any tasks scheduled at or before the current time.  May call
+  // |ScheduleNext| to schedule the next call to |Run|.
+  void Run();
+
+  void UpdateTime();
+  void ScheduleNext();
+
+  ControlledAlarmClock* alarm_;
+  sim_time_impl::SimulatedTimeControllerImpl impl_;
+
+  // Overrides the global rtc::Clock to ensure that it reports the same times as
+  // the time controller.
+  rtc::ScopedBaseFakeClock global_clock_;
+};
+
+}  // namespace webrtc
+
+#endif  // TEST_TIME_CONTROLLER_EXTERNAL_TIME_CONTROLLER_H_

test/time_controller/external_time_controller_unittest.cc

@@ -0,0 +1,181 @@
+/*
+ *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "test/time_controller/external_time_controller.h"
+
+#include <atomic>
+#include <memory>
+#include <utility>
+
+#include "rtc_base/event.h"
+#include "rtc_base/task_queue.h"
+#include "rtc_base/task_utils/repeating_task.h"
+#include "test/gmock.h"
+#include "test/gtest.h"
+
+// NOTE: Since these tests rely on real time behavior, they will be flaky
+// if run on heavily loaded systems.
+namespace webrtc {
+namespace {
+using ::testing::AtLeast;
+using ::testing::Invoke;
+using ::testing::MockFunction;
+using ::testing::NiceMock;
+using ::testing::Return;
+constexpr Timestamp kStartTime = Timestamp::Seconds<1000>();
+
+class FakeAlarm : public ControlledAlarmClock {
+ public:
+  explicit FakeAlarm(Timestamp start_time);
+
+  Clock* GetClock() override;
+  bool ScheduleAlarmAt(Timestamp deadline) override;
+  void SetCallback(std::function<void()> callback) override;
+  void Sleep(TimeDelta duration) override;
+
+ private:
+  SimulatedClock clock_;
+  Timestamp deadline_;
+  std::function<void()> callback_;
+};
+
+FakeAlarm::FakeAlarm(Timestamp start_time)
+    : clock_(start_time),
+      deadline_(Timestamp::PlusInfinity()),
+      callback_([] {}) {}
+
+Clock* FakeAlarm::GetClock() {
+  return &clock_;
+}
+
+bool FakeAlarm::ScheduleAlarmAt(Timestamp deadline) {
+  if (deadline < deadline_) {
+    deadline_ = deadline;
+    return true;
+  }
+  return false;
+}
+
+void FakeAlarm::SetCallback(std::function<void()> callback) {
+  callback_ = callback;
+}
+
+void FakeAlarm::Sleep(TimeDelta duration) {
+  Timestamp end_time = clock_.CurrentTime() + duration;
+
+  while (deadline_ <= end_time) {
+    clock_.AdvanceTime(deadline_ - clock_.CurrentTime());
+    deadline_ = Timestamp::PlusInfinity();
+    callback_();
+  }
+
+  clock_.AdvanceTime(end_time - clock_.CurrentTime());
+}
+
+}  // namespace
+
+TEST(ExternalTimeControllerTest, TaskIsStoppedOnStop) {
+  const TimeDelta kShortInterval = TimeDelta::ms(5);
+  const TimeDelta kLongInterval = TimeDelta::ms(20);
+  const int kShortIntervalCount = 4;
+  const int kMargin = 1;
+  FakeAlarm alarm(kStartTime);
+  ExternalTimeController time_simulation(&alarm);
+  rtc::TaskQueue task_queue(
+      time_simulation.GetTaskQueueFactory()->CreateTaskQueue(
+          "TestQueue", TaskQueueFactory::Priority::NORMAL));
+  std::atomic_int counter(0);
+  auto handle = RepeatingTaskHandle::Start(task_queue.Get(), [&] {
+    if (++counter >= kShortIntervalCount)
+      return kLongInterval;
+    return kShortInterval;
+  });
+  // Sleep long enough to go through the initial phase.
+  time_simulation.Sleep(kShortInterval * (kShortIntervalCount + kMargin));
+  EXPECT_EQ(counter.load(), kShortIntervalCount);
+
+  task_queue.PostTask(
+      [handle = std::move(handle)]() mutable { handle.Stop(); });
+
+  // Sleep long enough that the task would run at least once more if not
+  // stopped.
+  time_simulation.Sleep(kLongInterval * 2);
+  EXPECT_EQ(counter.load(), kShortIntervalCount);
+}
+
+TEST(ExternalTimeControllerTest, TaskCanStopItself) {
+  std::atomic_int counter(0);
+  FakeAlarm alarm(kStartTime);
+  ExternalTimeController time_simulation(&alarm);
+  rtc::TaskQueue task_queue(
+      time_simulation.GetTaskQueueFactory()->CreateTaskQueue(
+          "TestQueue", TaskQueueFactory::Priority::NORMAL));
+
+  RepeatingTaskHandle handle;
+  task_queue.PostTask([&] {
+    handle = RepeatingTaskHandle::Start(task_queue.Get(), [&] {
+      ++counter;
+      handle.Stop();
+      return TimeDelta::ms(2);
+    });
+  });
+  time_simulation.Sleep(TimeDelta::ms(10));
+  EXPECT_EQ(counter.load(), 1);
+}
+
+TEST(ExternalTimeControllerTest, YieldForTask) {
+  FakeAlarm alarm(kStartTime);
+  ExternalTimeController time_simulation(&alarm);
+
+  rtc::TaskQueue task_queue(
+      time_simulation.GetTaskQueueFactory()->CreateTaskQueue(
+          "TestQueue", TaskQueueFactory::Priority::NORMAL));
+
+  time_simulation.InvokeWithControlledYield([&] {
+    rtc::Event event;
+    task_queue.PostTask([&] { event.Set(); });
+    EXPECT_TRUE(event.Wait(200));
+  });
+}
+
+TEST(ExternalTimeControllerTest, TasksYieldToEachOther) {
+  FakeAlarm alarm(kStartTime);
+  ExternalTimeController time_simulation(&alarm);
+
+  rtc::TaskQueue task_queue(
+      time_simulation.GetTaskQueueFactory()->CreateTaskQueue(
+          "TestQueue", TaskQueueFactory::Priority::NORMAL));
+  rtc::TaskQueue other_queue(
+      time_simulation.GetTaskQueueFactory()->CreateTaskQueue(
+          "OtherQueue", TaskQueueFactory::Priority::NORMAL));
+
+  task_queue.PostTask([&] {
+    rtc::Event event;
+    other_queue.PostTask([&] { event.Set(); });
+    EXPECT_TRUE(event.Wait(200));
+  });
+
+  time_simulation.Sleep(TimeDelta::ms(300));
+}
+
+TEST(ExternalTimeControllerTest, CurrentTaskQueue) {
+  FakeAlarm alarm(kStartTime);
+  ExternalTimeController time_simulation(&alarm);
+
+  rtc::TaskQueue task_queue(
+      time_simulation.GetTaskQueueFactory()->CreateTaskQueue(
+          "TestQueue", TaskQueueFactory::Priority::NORMAL));
+
+  task_queue.PostTask([&] { EXPECT_TRUE(task_queue.IsCurrent()); });
+
+  time_simulation.Sleep(TimeDelta::ms(10));
+}
+
+}  // namespace webrtc

test/time_controller/real_time_controller.cc

@@ -39,6 +39,10 @@ void RealTimeController::InvokeWithControlledYield(
   closure();
 }
 
+rtc::YieldInterface* RealTimeController::YieldInterface() {
+  return nullptr;
+}
+
 RealTimeController* GlobalRealTimeController() {
   static RealTimeController* time_controller = new RealTimeController();
   return time_controller;

test/time_controller/real_time_controller.h

@@ -14,10 +14,10 @@
 #include <memory>
 
 #include "api/task_queue/task_queue_factory.h"
+#include "api/test/time_controller.h"
 #include "api/units/time_delta.h"
 #include "modules/utility/include/process_thread.h"
 #include "system_wrappers/include/clock.h"
-#include "test/time_controller/time_controller.h"
 
 namespace webrtc {
 class RealTimeController : public TimeController {
@@ -30,6 +30,7 @@ class RealTimeController : public TimeController {
       const char* thread_name) override;
   void Sleep(TimeDelta duration) override;
   void InvokeWithControlledYield(std::function<void()> closure) override;
+  rtc::YieldInterface* YieldInterface() override;
 
  private:
   std::unique_ptr<TaskQueueFactory> task_queue_factory_;

test/time_controller/simulated_time_controller.cc

@@ -440,6 +440,10 @@ void GlobalSimulatedTimeController::InvokeWithControlledYield(
   closure();
 }
 
+rtc::YieldInterface* GlobalSimulatedTimeController::YieldInterface() {
+  return &impl_;
+}
+
 // namespace sim_time_impl
 
 }  // namespace webrtc

test/time_controller/simulated_time_controller.h

@@ -16,6 +16,7 @@
 #include <utility>
 #include <vector>
 
+#include "api/test/time_controller.h"
 #include "api/units/timestamp.h"
 #include "modules/include/module.h"
 #include "modules/utility/include/process_thread.h"
@@ -24,7 +25,6 @@
 #include "rtc_base/platform_thread_types.h"
 #include "rtc_base/synchronization/yield_policy.h"
 #include "rtc_base/thread_checker.h"
-#include "test/time_controller/time_controller.h"
 
 namespace webrtc {
 
@@ -92,6 +92,7 @@ class GlobalSimulatedTimeController : public TimeController {
       const char* thread_name) override;
   void Sleep(TimeDelta duration) override;
   void InvokeWithControlledYield(std::function<void()> closure) override;
+  rtc::YieldInterface* YieldInterface() override;
 
  private:
   rtc::ScopedBaseFakeClock global_clock_;