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 <stddef.h>
9
10#include <deque>
11#include <memory>
12#include <queue>
13#include <vector>
14
15#include "base/callback.h"
16#include "base/callback_helpers.h"
17#include "base/macros.h"
18#include "base/single_thread_task_runner.h"
19#include "base/synchronization/lock.h"
20#include "base/test/test_pending_task.h"
21#include "base/threading/thread_checker_impl.h"
22#include "base/time/time.h"
23
24namespace base {
25
26class Clock;
27class TickClock;
28
29// Runs pending tasks in the order of the tasks' post time + delay, and keeps
30// track of a mock (virtual) tick clock time that can be fast-forwarded.
31//
32// TestMockTimeTaskRunner has the following properties:
33//
34//   - Methods RunsTasksOnCurrentThread() and Post[Delayed]Task() can be called
35//     from any thread, but the rest of the methods must be called on the same
36//     thread the TaskRunner was created on.
37//   - It allows for reentrancy, in that it handles the running of tasks that in
38//     turn call back into it (e.g., to post more tasks).
39//   - Tasks are stored in a priority queue, and executed in the increasing
40//     order of post time + delay, but ignoring nestability.
41//   - It does not check for overflow when doing time arithmetic. A sufficient
42//     condition for preventing overflows is to make sure that the sum of all
43//     posted task delays and fast-forward increments is still representable by
44//     a TimeDelta, and that adding this delta to the starting values of Time
45//     and TickTime is still within their respective range.
46//   - Tasks aren't guaranteed to be destroyed immediately after they're run.
47//
48// This is a slightly more sophisticated version of TestSimpleTaskRunner, in
49// that it supports running delayed tasks in the correct temporal order.
50class TestMockTimeTaskRunner : public SingleThreadTaskRunner {
51 public:
52  // Everything that is executed in the scope of a ScopedContext will behave as
53  // though it ran under |scope| (i.e. ThreadTaskRunnerHandle,
54  // RunsTasksOnCurrentThread, etc.). This allows the test body to be all in one
55  // block when multiple TestMockTimeTaskRunners share the main thread. For
56  // example:
57  //
58  //   class ExampleFixture {
59  //    protected:
60  //     DoBarOnFoo() {
61  //       DCHECK(foo_task_runner_->RunsOnCurrentThread());
62  //       EXPECT_EQ(foo_task_runner_, ThreadTaskRunnerHandle::Get());
63  //       DoBar();
64  //     }
65  //
66  //     // Mock main task runner.
67  //     base::MessageLoop message_loop_;
68  //     base::ScopedMockTimeMessageLoopTaskRunner main_task_runner_;
69  //
70  //     // Mock foo task runner.
71  //     scoped_refptr<TestMockTimeTaskRunner> foo_task_runner_ =
72  //         new TestMockTimeTaskRunner();
73  //   };
74  //
75  //   TEST_F(ExampleFixture, DoBarOnFoo) {
76  //     DoThingsOnMain();
77  //     {
78  //       TestMockTimeTaskRunner::ScopedContext scoped_context(
79  //           foo_task_runner_.get());
80  //       DoBarOnFoo();
81  //     }
82  //     DoMoreThingsOnMain();
83  //   }
84  //
85  class ScopedContext {
86   public:
87    // Note: |scope| is ran until idle as part of this constructor to ensure
88    // that anything which runs in the underlying scope runs after any already
89    // pending tasks (the contrary would break the SequencedTraskRunner
90    // contract).
91    explicit ScopedContext(scoped_refptr<TestMockTimeTaskRunner> scope);
92    ~ScopedContext();
93
94   private:
95    ScopedClosureRunner on_destroy_;
96    DISALLOW_COPY_AND_ASSIGN(ScopedContext);
97  };
98
99  // Constructs an instance whose virtual time will start at the Unix epoch, and
100  // whose time ticks will start at zero.
101  TestMockTimeTaskRunner();
102
103  // Constructs an instance starting at the given virtual time and time ticks.
104  TestMockTimeTaskRunner(Time start_time, TimeTicks start_ticks);
105
106  // Fast-forwards virtual time by |delta|, causing all tasks with a remaining
107  // delay less than or equal to |delta| to be executed. |delta| must be
108  // non-negative.
109  void FastForwardBy(TimeDelta delta);
110
111  // Fast-forwards virtual time just until all tasks are executed.
112  void FastForwardUntilNoTasksRemain();
113
114  // Executes all tasks that have no remaining delay. Tasks with a remaining
115  // delay greater than zero will remain enqueued, and no virtual time will
116  // elapse.
117  void RunUntilIdle();
118
119  // Clears the queue of pending tasks without running them.
120  void ClearPendingTasks();
121
122  // Returns the current virtual time (initially starting at the Unix epoch).
123  Time Now() const;
124
125  // Returns the current virtual tick time (initially starting at 0).
126  TimeTicks NowTicks() const;
127
128  // Returns a Clock that uses the virtual time of |this| as its time source.
129  // The returned Clock will hold a reference to |this|.
130  std::unique_ptr<Clock> GetMockClock() const;
131
132  // Returns a TickClock that uses the virtual time ticks of |this| as its tick
133  // source. The returned TickClock will hold a reference to |this|.
134  std::unique_ptr<TickClock> GetMockTickClock() const;
135
136  std::deque<TestPendingTask> TakePendingTasks();
137  bool HasPendingTask() const;
138  size_t GetPendingTaskCount() const;
139  TimeDelta NextPendingTaskDelay() const;
140
141  // SingleThreadTaskRunner:
142  bool RunsTasksOnCurrentThread() const override;
143  bool PostDelayedTask(const tracked_objects::Location& from_here,
144                       OnceClosure task,
145                       TimeDelta delay) override;
146  bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
147                                  OnceClosure task,
148                                  TimeDelta delay) override;
149
150 protected:
151  ~TestMockTimeTaskRunner() override;
152
153  // Whether the elapsing of virtual time is stopped or not. Subclasses can
154  // override this method to perform early exits from a running task runner.
155  // Defaults to always return false.
156  virtual bool IsElapsingStopped();
157
158  // Called before the next task to run is selected, so that subclasses have a
159  // last chance to make sure all tasks are posted.
160  virtual void OnBeforeSelectingTask();
161
162  // Called after the current mock time has been incremented so that subclasses
163  // can react to the passing of time.
164  virtual void OnAfterTimePassed();
165
166  // Called after each task is run so that subclasses may perform additional
167  // activities, e.g., pump additional task runners.
168  virtual void OnAfterTaskRun();
169
170 private:
171  struct TestOrderedPendingTask;
172
173  // Predicate that defines a strict weak temporal ordering of tasks.
174  class TemporalOrder {
175   public:
176    bool operator()(const TestOrderedPendingTask& first_task,
177                    const TestOrderedPendingTask& second_task) const;
178  };
179
180  typedef std::priority_queue<TestOrderedPendingTask,
181                              std::vector<TestOrderedPendingTask>,
182                              TemporalOrder> TaskPriorityQueue;
183
184  // Core of the implementation for all flavors of fast-forward methods. Given a
185  // non-negative |max_delta|, runs all tasks with a remaining delay less than
186  // or equal to |max_delta|, and moves virtual time forward as needed for each
187  // processed task. Pass in TimeDelta::Max() as |max_delta| to run all tasks.
188  void ProcessAllTasksNoLaterThan(TimeDelta max_delta);
189
190  // Forwards |now_ticks_| until it equals |later_ticks|, and forwards |now_| by
191  // the same amount. Calls OnAfterTimePassed() if |later_ticks| > |now_ticks_|.
192  // Does nothing if |later_ticks| <= |now_ticks_|.
193  void ForwardClocksUntilTickTime(TimeTicks later_ticks);
194
195  // Returns the |next_task| to run if there is any with a running time that is
196  // at most |reference| + |max_delta|. This additional complexity is required
197  // so that |max_delta| == TimeDelta::Max() can be supported.
198  bool DequeueNextTask(const TimeTicks& reference,
199                       const TimeDelta& max_delta,
200                       TestPendingTask* next_task);
201
202  // Also used for non-dcheck logic (RunsTasksOnCurrentThread()) and as such
203  // needs to be a ThreadCheckerImpl.
204  ThreadCheckerImpl thread_checker_;
205
206  Time now_;
207  TimeTicks now_ticks_;
208
209  // Temporally ordered heap of pending tasks. Must only be accessed while the
210  // |tasks_lock_| is held.
211  TaskPriorityQueue tasks_;
212
213  // The ordinal to use for the next task. Must only be accessed while the
214  // |tasks_lock_| is held.
215  size_t next_task_ordinal_;
216
217  Lock tasks_lock_;
218
219  DISALLOW_COPY_AND_ASSIGN(TestMockTimeTaskRunner);
220};
221
222}  // namespace base
223
224#endif  // BASE_TEST_TEST_MOCK_TIME_TASK_RUNNER_H_
225