Make SequencedWorkerPool a TaskRunner

base/task_runner_unittest.h

+// Copyright (c) 2012 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.
+
+// This class defines tests that implementations of TaskRunner should
+// pass in order to be conformant.  Here's how you use it to test your
+// implementation.
+//
+// Say your class is called MyTaskRunner.  Then you need to define a
+// class called MyTaskRunnerTestDelegate in my_task_runner_unittest.cc
+// like this:
+//
+//   class MyTaskRunnerTestDelegate {
+//    public:
+//     // Tasks posted to the task runner after this and before
+//     // StopTaskRunner() is called is called should run successfully.
+//     void StartTaskRunner() {
+//       ...
+//     }
+//
+//     // Should return the task runner implementation.  Only called
+//     // after StartTaskRunner and before StopTaskRunner.
+//     scoped_refptr<MyTaskRunner> GetTaskRunner() {
+//       ...
+//     }
+//
+//     // Stop the task runner and make sure all tasks posted before
+//     // this is called are run.
+//     void StopTaskRunner() {
+//       ...
+//     }
+//   };
+//
+// The TaskRunnerTest test harness will have a member variable of
+// this delegate type and will call its functions in the various
+// tests.
+//
+// Then you simply #include this file as well as gtest.h and add the
+// following statement to my_task_runner_unittest.cc:
+//
+//   INSTANTIATE_TYPED_TEST_CASE_P(
+//       MyTaskRunner, TaskRunnerTest, MyTaskRunnerTestDelegate);
+//
+// Easy!
+
+#ifndef BASE_MEMORY_TASK_RUNNER_UNITTEST_H_
+#define BASE_MEMORY_TASK_RUNNER_UNITTEST_H_
+#pragma once
+
+#include <cstddef>
+#include <map>
+
+#include "base/basictypes.h"
+#include "base/bind.h"
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
+#include "base/task_runner.h"
+#include "base/tracked_objects.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+
+// Utility class used in the tests below.
+class TaskTracker : public RefCountedThreadSafe<TaskTracker> {
+ public:
+  TaskTracker();
+
+  void RunTask(int i);
+
+  std::map<int, int> GetTaskRunCounts() const;
+
+ private:
+  friend class RefCountedThreadSafe<TaskTracker>;
+
+  ~TaskTracker();
+
+  mutable Lock task_run_counts_lock_;
+  std::map<int, int> task_run_counts_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskTracker);
+};
+
+template <typename TaskRunnerTestDelegate>
+class TaskRunnerTest : public testing::Test {
+ protected:
+  TaskRunnerTest() : task_tracker_(new TaskTracker()) {}
+
+  const scoped_refptr<TaskTracker> task_tracker_;
+  TaskRunnerTestDelegate delegate_;
+};
+
+TYPED_TEST_CASE_P(TaskRunnerTest);
+
+// We can't really test much, since TaskRunner provides very few
+// guarantees.
+
+// Post a bunch of tasks to the task runner.  They should all
+// complete.
+TYPED_TEST_P(TaskRunnerTest, Basic) {
+  std::map<int, int> expected_task_run_counts;
+
+  this->delegate_.StartTaskRunner();
+  scoped_refptr<TaskRunner> task_runner = this->delegate_.GetTaskRunner();
+  for (int i = 0; i < 20; ++i) {

[willchan no longer on Chromium, 2012/02/23 19:39:57]

Add comments explaining what the two loops are doing. It wasn't immediately
obvious we were running task 1 one time, task 2 two times, etc.

[akalin, 2012/02/23 22:52:21]

Done.

+    Closure task = Bind(&TaskTracker::RunTask, this->task_tracker_, i);
+    for (int j = 0; j < i + 1; ++j) {
+      task_runner->PostTask(FROM_HERE, task);
+      ++expected_task_run_counts[i];
+    }
+  }
+  this->delegate_.StopTaskRunner();

[willchan no longer on Chromium, 2012/02/23 19:39:57]

I don't know that this is correct. There's no guarantee that when the TaskRunner
is stopped that it needs to execute all the tasks left in its task queue.
Perhaps the test should only call this after it detects that all tasks have
finished running.

[akalin, 2012/02/23 22:52:21]

It should be the job of the delegate class to do the detection that all tasks
have finished running (if needed).  I think that's covered by the comments at
the top re. the delegates.

+
+  EXPECT_EQ(expected_task_run_counts,
+            this->task_tracker_->GetTaskRunCounts());
+}
+
+// Post a bunch of delayed tasks to the task runner.  They should all
+// complete.
+TYPED_TEST_P(TaskRunnerTest, Delayed) {
+  std::map<int, int> expected_task_run_counts;
+
+  this->delegate_.StartTaskRunner();
+  scoped_refptr<TaskRunner> task_runner = this->delegate_.GetTaskRunner();
+  for (int i = 0; i < 20; ++i) {
+    Closure task = Bind(&TaskTracker::RunTask, this->task_tracker_, i);
+    for (int j = 0; j < i + 1; ++j) {
+      task_runner->PostDelayedTask(FROM_HERE, task, j);
+      ++expected_task_run_counts[i];
+    }
+  }
+  this->delegate_.StopTaskRunner();
+
+  EXPECT_EQ(expected_task_run_counts,
+            this->task_tracker_->GetTaskRunCounts());
+}
+
+REGISTER_TYPED_TEST_CASE_P(TaskRunnerTest, Basic, Delayed);
+

[willchan no longer on Chromium, 2012/02/23 19:39:57]

We should add TODOs for future tests to verify RunsTaskOnCurrentThread() returns
true for Tasks run on the TaskRunner. And then spawn a PlatformThread that
checks RunsTaskOnCurrentThread() returns false for the TaskRunner on that new
thread.

[akalin, 2012/02/23 22:52:21]

Done.

+}  // namespace base
+
+#endif  // BASE_MEMORY_REF_COUNTED_H_