Add TestMockTimeTaskRunner in base/test.

base/test/test_mock_time_task_runner.h

+// Copyright 2015 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.
+
+#ifndef BASE_TEST_TEST_MOCK_TIME_TASK_RUNNER_H_
+#define BASE_TEST_TEST_MOCK_TIME_TASK_RUNNER_H_
+
+#include <queue>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/single_thread_task_runner.h"
+#include "base/synchronization/lock.h"
+#include "base/test/test_pending_task.h"
+#include "base/threading/thread_checker.h"
+#include "base/time/tick_clock.h"
+#include "base/time/time.h"
+
+namespace base {
+
+// Runs pending tasks in the order of the tasks' post time + delay, and keeps
+// track of a mock (virtual) tick clock time that can be fast-forwarded.
+//
+// TestMockTimeTaskRunner has the following properties:
+//
+//   - Methods RunsTasksOnCurrentThread() and Post[Delayed]Task() can be called
+//     from any thread, but the rest of the methods must be called on the same
+//     thread the TaskRunner was created on.
+//   - It allows for reentrancy, in that it handles the running of tasks that in
+//     turn call back into it (e.g., to post more tasks).
+//   - Tasks are stored in a priority queue, and executed in the increasing
+//     order of post time + delay.
+//   - Non-nestable tasks are not supported.
+//   - Tasks aren't guaranteed to be destroyed immediately after they're run.
+//
+// This is a slightly more sophisticated version of TestSimpleTaskRunner, in
+// that it supports running delayed tasks in the correct temporal order.
+class TestMockTimeTaskRunner : public base::SingleThreadTaskRunner {
+ public:
+  TestMockTimeTaskRunner();
+
+  // Fast-forwards virtual time by |delta|, causing all tasks with a remaining
+  // delay less than or equal to |delta| to be executed.
+  void FastForwardBy(base::TimeDelta delta);
+
+  // Fast-forwards virtual time just until all tasks are executed.
+  void FastForwardUntilNoTasksRemain();
+
+  // Executes all tasks that have no remaining delay. Tasks with a remaining
+  // delay greater than zero will remain enqueued, and no virtual time will
+  // elapse.
+  void RunUntilIdle();
+
+  // Returns the current virtual time.
+  TimeTicks GetCurrentMockTime() const;
+
+  // Returns a TickClock that uses the mock time of |this| as its time source.
+  // The returned TickClock will hold a reference to |this|.
+  scoped_ptr<TickClock> GetMockTickClock() const;
+
+  bool HasPendingTask() const;
+  TimeDelta NextPendingTaskDelay() const;
+
+  // SingleThreadTaskRunner:
+  bool RunsTasksOnCurrentThread() const override;
+  bool PostDelayedTask(const tracked_objects::Location& from_here,
+                               const base::Closure& task,
+                               TimeDelta delay) override;
+  bool PostNonNestableDelayedTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task,
+      TimeDelta delay) override;
+
+ protected:
+  ~TestMockTimeTaskRunner() override;
+
+  // Called before the next task to run is selected, so that subclasses have a
+  // last chance to make sure all tasks are posted.
+  virtual void OnBeforeSelectingTask();
+
+  // Called after the current mock time has been incremented so that subclasses
+  // can react to the passing of time.
+  virtual void OnAfterTimePassed();
+
+  // Called after each task is run so that subclasses may perform additional
+  // activities, e.g., pump additional task runners.
+  virtual void OnAfterTaskRun();
+
+ private:
+  // Predicate that defines a strict weak temporal ordering of tasks.
+  class TemporalOrder {
+   public:
+    bool operator()(const TestPendingTask& first_task,
+                    const TestPendingTask& second_task) const;
+  };
+
+  typedef std::priority_queue<TestPendingTask,
+                              std::vector<TestPendingTask>,
+                              TemporalOrder> TaskPriorityQueue;
+
+  // Returns the |next_task| to run if there is any with a running time that is
+  // at most |reference| + |max_delta|. This additional complexity is required
+  // so that |max_delta| == TimeDelta::Max() can be supported.
+  bool DequeueNextTask(const base::TimeTicks& reference,
+                       const base::TimeDelta& max_delta,
+                       TestPendingTask* next_task);
+
+  base::ThreadChecker thread_checker_;
+  base::TimeTicks now_;
+
+  // Temporally ordered heap of pending tasks. Must only be accessed while the
+  // |tasks_lock_| is held.
+  TaskPriorityQueue tasks_;
+  base::Lock tasks_lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestMockTimeTaskRunner);
+};
+
+}  // namespace base
+
+#endif  // BASE_TEST_TEST_MOCK_TIME_TASK_RUNNER_H_