Fixing and enhancing OrderedSimpleTaskRunner to allow 100% deterministic tests.

cc/test/ordered_simple_task_runner.h

Index: cc/test/ordered_simple_task_runner.h
diff --git a/cc/test/ordered_simple_task_runner.h b/cc/test/ordered_simple_task_runner.h
index 8850a760bf88de7fb7f7df663324271809d3e8c2..0f903e1eb8542704d8fc8244b1aac153132ade24 100644
--- a/cc/test/ordered_simple_task_runner.h
+++ b/cc/test/ordered_simple_task_runner.h
@@ -5,24 +5,144 @@
 #ifndef CC_TEST_ORDERED_SIMPLE_TASK_RUNNER_H_
 #define CC_TEST_ORDERED_SIMPLE_TASK_RUNNER_H_
 
+#include <limits>
+#include <set>
+#include <vector>
+
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/debug/trace_event.h"
+#include "base/logging.h"
 #include "base/test/test_simple_task_runner.h"
+#include "cc/test/test_now_source.h"
 
 namespace cc {
 
+// Subclass of TestPendingTask which has a unique ID for every task, supports
+// being used inside a std::set and has debug tracing support.
+class TestOrderablePendingTask : public base::TestPendingTask {
+ public:
+  TestOrderablePendingTask();
+  TestOrderablePendingTask(const tracked_objects::Location& location,
+                           const base::Closure& task,
+                           base::TimeTicks post_time,
+                           base::TimeDelta delay,
+                           TestNestability nestability);
+  ~TestOrderablePendingTask();
+
+  // operators needed by std::set and comparison
+  bool operator==(const TestOrderablePendingTask& other) const;
+  bool operator<(const TestOrderablePendingTask& other) const;
+
+  // debug tracing functions
+  scoped_refptr<base::debug::ConvertableToTraceFormat> AsValue() const;
+  void AsValueInto(base::debug::TracedValue* state) const;
+
+ private:
+  static size_t task_id_counter;
+  const size_t task_id_;
+};
+
 // This runs pending tasks based on task's post_time + delay.
 // We should not execute a delayed task sooner than some of the queued tasks
 // which don't have a delay even though it is queued early.
-class OrderedSimpleTaskRunner : public base::TestSimpleTaskRunner {
+class OrderedSimpleTaskRunner : public base::SingleThreadTaskRunner {
  public:
   OrderedSimpleTaskRunner();
+  OrderedSimpleTaskRunner(scoped_refptr<TestNowSource> now_src,
+                          bool advance_now);
+
+  // base::TestSimpleTaskRunner implementation:
+  virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
+                               const base::Closure& task,
+                               base::TimeDelta delay) OVERRIDE;
+  virtual bool PostNonNestableDelayedTask(
+      const tracked_objects::Location& from_here,
+      const base::Closure& task,
+      base::TimeDelta delay) OVERRIDE;
+
+  virtual bool RunsTasksOnCurrentThread() const OVERRIDE;
+
+  // Set a maximum number of tasks to run at once. Useful as a timeout to
+  // prevent infinite task loops.
+  static const size_t kAbsoluteMaxTasks;
+  void SetRunTaskLimit(size_t max_tasks) { max_tasks_ = max_tasks; }
+  void ClearRunTaskLimit() { max_tasks_ = kAbsoluteMaxTasks; }
+
+  // Allow task runner to advance now when running tasks.
+  void SetAutoAdvanceNowToPendingTasks(bool advance_now) {
+    advance_now_ = advance_now;
+  }
+
+  base::TimeTicks NextTaskTime();
+  base::TimeDelta DelayToNextTaskTime();
+
+  // Run tasks while the callback returns true or too many tasks have been run.
+  // Returns true if there are still pending tasks left.
+  bool RunTasks(base::Callback<bool(void)> condition);

[brianderson, 2014/09/05 02:48:03]

If we rename this to RunTasksWhile we could remove "While" from the functions
that create the conditions and it will communicate better what this method does
with the condition.

[mithro-old, 2014/09/08 12:52:20]

Done.

 
-  virtual void RunPendingTasks() OVERRIDE;
+  // Run tasks while *all* of the callbacks return true or too many tasks have
+  // been run. Exits on the *first* condition which returns false, skipping
+  // calling all remaining condition.
+  // Returns true if there are still pending tasks left.
+  bool RunTasks(const std::vector<base::Callback<bool(void)> >& conditions);
+
+  // Convenience functions to run tasks to common conditions
+
+  // Run tasks which existed at the start of this call.
+  // Return code indicates tasks still exist to run.
+  bool RunPendingTasks();
+  // Keep running tasks until no tasks are left.
+  // Return code indicates tasks still exist to run which also indicates if
+  // runner reached idle.
+  bool RunUntilIdle();
+  // Keep running tasks until given time period.
+  // Return code indicates tasks still exist to run.
+  bool RunUntilTime(base::TimeTicks time);
+  bool RunForPeriod(base::TimeDelta period);
+
+  // base::debug tracing functionality
+  scoped_refptr<base::debug::ConvertableToTraceFormat> AsValue() const;
+  virtual void AsValueInto(base::debug::TracedValue* state) const;
+
+  // Common conditions to run for, exposed publicly to allow external users to
+  // use their own combinations.
+  // -------------------------------------------------------------------------
+
+  // Keep running until the given number of tasks have run.
+  // You generally shouldn't use this check as it will cause your tests to fail
+  // when code is changed adding a new task. It is useful as a "timeout" type
+  // solution.
+  base::Callback<bool(void)> WhileTaskRunCountBelow(size_t max_tasks);
+
+  // Keep running until a task which didn't exist initially would run.
+  base::Callback<bool(void)> WhileTaskExistedInitially();
+
+  // Stop running tasks when NextTaskTime() >= stop_at
+  base::Callback<bool(void)> WhileNowBefore(base::TimeTicks stop_at);
+
+  // Advance Now() to the next task to run.
+  base::Callback<bool(void)> AdvanceNow();
 
  protected:
+  bool WhileTaskRunCountBelowCallback(size_t max_tasks, size_t* task_run);
+  bool WhileTaskExistedInitiallyCallback(
+      const std::set<TestOrderablePendingTask>& existing_tasks);
+  bool WhileNowBeforeCallback(base::TimeTicks stop_at);
+  bool AdvanceNowCallback();
+
   virtual ~OrderedSimpleTaskRunner();
 
+  base::ThreadChecker thread_checker_;
+
+  bool advance_now_;
+  scoped_refptr<TestNowSource> now_src_;
+
+  size_t max_tasks_;
+
+  bool inside_run_tasks_until_;
+  std::set<TestOrderablePendingTask> pending_tasks_;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(OrderedSimpleTaskRunner);
 };