base/test/test_mock_time_task_runner.h

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_TEST_TEST_MOCK_TIME_TASK_RUNNER_H_
   6 #define BASE_TEST_TEST_MOCK_TIME_TASK_RUNNER_H_
   7
   8 #include <queue>
   9 #include <vector>
  10
  11 #include "base/macros.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "base/single_thread_task_runner.h"
  14 #include "base/synchronization/lock.h"
  15 #include "base/test/test_pending_task.h"
  16 #include "base/threading/thread_checker.h"
  17 #include "base/time/time.h"
  18
  19 namespace base {
  20
  21 class Clock;
  22 class TickClock;
  23
  24 // Runs pending tasks in the order of the tasks' post time + delay, and keeps
  25 // track of a mock (virtual) tick clock time that can be fast-forwarded.
  26 //
  27 // TestMockTimeTaskRunner has the following properties:
  28 //
  29 //   - Methods RunsTasksOnCurrentThread() and Post[Delayed]Task() can be called
  30 //     from any thread, but the rest of the methods must be called on the same
  31 //     thread the TaskRunner was created on.
  32 //   - It allows for reentrancy, in that it handles the running of tasks that in
  33 //     turn call back into it (e.g., to post more tasks).
  34 //   - Tasks are stored in a priority queue, and executed in the increasing
  35 //     order of post time + delay, but ignoring nestability.
  36 //   - It does not check for overflow when doing time arithmetic. A sufficient
  37 //     condition for preventing overflows is to make sure that the sum of all
  38 //     posted task delays and fast-forward increments is still representable by
  39 //     a TimeDelta, and that adding this delta to the starting values of Time
  40 //     and TickTime is still within their respective range.
  41 //   - Tasks aren't guaranteed to be destroyed immediately after they're run.
  42 //
  43 // This is a slightly more sophisticated version of TestSimpleTaskRunner, in
  44 // that it supports running delayed tasks in the correct temporal order.
  45 class TestMockTimeTaskRunner : public SingleThreadTaskRunner {
  46  public:
  47   // Constructs an instance whose virtual time will start at the Unix epoch, and
  48   // whose time ticks will start at zero.
  49   TestMockTimeTaskRunner();
  50
  51   // Fast-forwards virtual time by |delta|, causing all tasks with a remaining
  52   // delay less than or equal to |delta| to be executed. |delta| must be
  53   // non-negative.
  54   void FastForwardBy(TimeDelta delta);
  55
  56   // Fast-forwards virtual time just until all tasks are executed.
  57   void FastForwardUntilNoTasksRemain();
  58
  59   // Executes all tasks that have no remaining delay. Tasks with a remaining
  60   // delay greater than zero will remain enqueued, and no virtual time will
  61   // elapse.
  62   void RunUntilIdle();
  63
  64   // Clears the queue of pending tasks without running them.
  65   void ClearPendingTasks();
  66
  67   // Returns the current virtual time (initially starting at the Unix epoch).
  68   Time Now() const;
  69
  70   // Returns the current virtual tick time (initially starting at 0).
  71   TimeTicks NowTicks() const;
  72
  73   // Returns a Clock that uses the virtual time of |this| as its time source.
  74   // The returned Clock will hold a reference to |this|.
  75   scoped_ptr<Clock> GetMockClock() const;
  76
  77   // Returns a TickClock that uses the virtual time ticks of |this| as its tick
  78   // source. The returned TickClock will hold a reference to |this|.
  79   scoped_ptr<TickClock> GetMockTickClock() const;
  80
  81   bool HasPendingTask() const;
  82   size_t GetPendingTaskCount() const;
  83   TimeDelta NextPendingTaskDelay() const;
  84
  85   // SingleThreadTaskRunner:
  86   bool RunsTasksOnCurrentThread() const override;
  87   bool PostDelayedTask(const tracked_objects::Location& from_here,
  88                        const Closure& task,
  89                        TimeDelta delay) override;
  90   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
  91                                   const Closure& task,
  92                                   TimeDelta delay) override;
  93
  94  protected:
  95   ~TestMockTimeTaskRunner() override;
  96
  97   // Whether the elapsing of virtual time is stopped or not. Subclasses can
  98   // override this method to perform early exits from a running task runner.
  99   // Defaults to always return false.
 100   virtual bool IsElapsingStopped();
 101
 102   // Called before the next task to run is selected, so that subclasses have a
 103   // last chance to make sure all tasks are posted.
 104   virtual void OnBeforeSelectingTask();
 105
 106   // Called after the current mock time has been incremented so that subclasses
 107   // can react to the passing of time.
 108   virtual void OnAfterTimePassed();
 109
 110   // Called after each task is run so that subclasses may perform additional
 111   // activities, e.g., pump additional task runners.
 112   virtual void OnAfterTaskRun();
 113
 114  private:
 115   // Predicate that defines a strict weak temporal ordering of tasks.
 116   class TemporalOrder {
 117    public:
 118     bool operator()(const TestPendingTask& first_task,
 119                     const TestPendingTask& second_task) const;
 120   };
 121
 122   typedef std::priority_queue<TestPendingTask,
 123                               std::vector<TestPendingTask>,
 124                               TemporalOrder> TaskPriorityQueue;
 125
 126   // Core of the implementation for all flavors of fast-forward methods. Given a
 127   // non-negative |max_delta|, runs all tasks with a remaining delay less than
 128   // or equal to |max_delta|, and moves virtual time forward as needed for each
 129   // processed task. Pass in TimeDelta::Max() as |max_delta| to run all tasks.
 130   void ProcessAllTasksNoLaterThan(TimeDelta max_delta);
 131
 132   // Forwards |now_ticks_| until it equals |later_ticks|, and forwards |now_| by
 133   // the same amount. Calls OnAfterTimePassed() if |later_ticks| > |now_ticks_|.
 134   // Does nothing if |later_ticks| <= |now_ticks_|.
 135   void ForwardClocksUntilTickTime(TimeTicks later_ticks);
 136
 137   // Returns the |next_task| to run if there is any with a running time that is
 138   // at most |reference| + |max_delta|. This additional complexity is required
 139   // so that |max_delta| == TimeDelta::Max() can be supported.
 140   bool DequeueNextTask(const TimeTicks& reference,
 141                        const TimeDelta& max_delta,
 142                        TestPendingTask* next_task);
 143
 144   ThreadChecker thread_checker_;
 145   Time now_;
 146   TimeTicks now_ticks_;
 147
 148   // Temporally ordered heap of pending tasks. Must only be accessed while the
 149   // |tasks_lock_| is held.
 150   TaskPriorityQueue tasks_;
 151   Lock tasks_lock_;
 152
 153   DISALLOW_COPY_AND_ASSIGN(TestMockTimeTaskRunner);
 154 };
 155
 156 }  // namespace base
 157
 158 #endif  // BASE_TEST_TEST_MOCK_TIME_TASK_RUNNER_H_