1 files changed, 727 insertions, 0 deletions
diff --git a/third_party/python/futures/test_futures.py b/third_party/python/futures/test_futures.py
new file mode 100644
index 0000000000..301cd0a934
--- /dev/null
+++ b/third_party/python/futures/test_futures.py
@@ -0,0 +1,727 @@
+import os
+import subprocess
+import sys
+import threading
+import functools
+import contextlib
+import logging
+import re
+import time
+import gc
+from StringIO import StringIO
+from test import test_support
+
+from concurrent import futures
+from concurrent.futures._base import (
+    PENDING, RUNNING, CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED, Future)
+
+try:
+    import unittest2 as unittest
+except ImportError:
+    import unittest
+
+
+def reap_threads(func):
+    """Use this function when threads are being used.  This will
+    ensure that the threads are cleaned up even when the test fails.
+    If threading is unavailable this function does nothing.
+    """
+    @functools.wraps(func)
+    def decorator(*args): 
+        key = test_support.threading_setup()
+        try:
+            return func(*args)
+        finally:
+            test_support.threading_cleanup(*key)
+    return decorator
+
+
+# Executing the interpreter in a subprocess
+def _assert_python(expected_success, *args, **env_vars):
+    cmd_line = [sys.executable]
+    if not env_vars:
+        cmd_line.append('-E')
+    # Need to preserve the original environment, for in-place testing of
+    # shared library builds.
+    env = os.environ.copy()
+    # But a special flag that can be set to override -- in this case, the
+    # caller is responsible to pass the full environment.
+    if env_vars.pop('__cleanenv', None):
+        env = {}
+    env.update(env_vars) 
+    cmd_line.extend(args)
+    p = subprocess.Popen(cmd_line, stdin=subprocess.PIPE,
+                         stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                         env=env)
+    try:
+        out, err = p.communicate()
+    finally:
+        subprocess._cleanup()
+        p.stdout.close()
+        p.stderr.close()
+    rc = p.returncode
+    err = strip_python_stderr(err)
+    if (rc and expected_success) or (not rc and not expected_success):
+        raise AssertionError(
+            "Process return code is %d, "
+            "stderr follows:\n%s" % (rc, err.decode('ascii', 'ignore')))
+    return rc, out, err
+
+
+def assert_python_ok(*args, **env_vars):
+    """
+    Assert that running the interpreter with `args` and optional environment
+    variables `env_vars` is ok and return a (return code, stdout, stderr) tuple.
+    """
+    return _assert_python(True, *args, **env_vars)
+
+
+def strip_python_stderr(stderr): 
+    """Strip the stderr of a Python process from potential debug output
+    emitted by the interpreter.
+
+    This will typically be run on the result of the communicate() method
+    of a subprocess.Popen object.
+    """
+    stderr = re.sub(r"\[\d+ refs\]\r?\n?$".encode(), "".encode(), stderr).strip()
+    return stderr
+
+
+@contextlib.contextmanager
+def captured_stderr():
+    """Return a context manager used by captured_stdout/stdin/stderr
+    that temporarily replaces the sys stream *stream_name* with a StringIO."""
+    logging_stream = StringIO()
+    handler = logging.StreamHandler(logging_stream)
+    logging.root.addHandler(handler)
+
+    try:
+        yield logging_stream
+    finally:
+        logging.root.removeHandler(handler)
+
+
+def create_future(state=PENDING, exception=None, result=None):
+    f = Future()
+    f._state = state
+    f._exception = exception
+    f._result = result
+    return f
+
+
+PENDING_FUTURE = create_future(state=PENDING)
+RUNNING_FUTURE = create_future(state=RUNNING)
+CANCELLED_FUTURE = create_future(state=CANCELLED)
+CANCELLED_AND_NOTIFIED_FUTURE = create_future(state=CANCELLED_AND_NOTIFIED)
+EXCEPTION_FUTURE = create_future(state=FINISHED, exception=IOError())
+SUCCESSFUL_FUTURE = create_future(state=FINISHED, result=42)
+
+
+def mul(x, y):
+    return x * y
+
+
+def sleep_and_raise(t):
+    time.sleep(t)
+    raise Exception('this is an exception')
+
+def sleep_and_print(t, msg):
+    time.sleep(t)
+    print(msg)
+    sys.stdout.flush()
+
+
+class ExecutorMixin:
+    worker_count = 5
+
+    def setUp(self):
+        self.t1 = time.time()
+        try:
+            self.executor = self.executor_type(max_workers=self.worker_count)
+        except NotImplementedError:
+            e = sys.exc_info()[1]
+            self.skipTest(str(e))
+        self._prime_executor()
+
+    def tearDown(self):
+        self.executor.shutdown(wait=True)
+        dt = time.time() - self.t1
+        if test_support.verbose:
+            print("%.2fs" % dt)
+        self.assertLess(dt, 60, "synchronization issue: test lasted too long")
+
+    def _prime_executor(self):
+        # Make sure that the executor is ready to do work before running the
+        # tests. This should reduce the probability of timeouts in the tests.
+        futures = [self.executor.submit(time.sleep, 0.1)
+                   for _ in range(self.worker_count)]
+
+        for f in futures:
+            f.result()
+
+
+class ThreadPoolMixin(ExecutorMixin):
+    executor_type = futures.ThreadPoolExecutor
+
+
+class ProcessPoolMixin(ExecutorMixin):
+    executor_type = futures.ProcessPoolExecutor
+
+
+class ExecutorShutdownTest(unittest.TestCase):
+    def test_run_after_shutdown(self):
+        self.executor.shutdown()
+        self.assertRaises(RuntimeError,
+                          self.executor.submit,
+                          pow, 2, 5)
+
+    def test_interpreter_shutdown(self):
+        # Test the atexit hook for shutdown of worker threads and processes
+        rc, out, err = assert_python_ok('-c', """if 1:
+            from concurrent.futures import %s
+            from time import sleep
+            from test_futures import sleep_and_print
+            t = %s(5)
+            t.submit(sleep_and_print, 1.0, "apple")
+            """ % (self.executor_type.__name__, self.executor_type.__name__))
+        # Errors in atexit hooks don't change the process exit code, check
+        # stderr manually.
+        self.assertFalse(err)
+        self.assertEqual(out.strip(), "apple".encode())
+
+    def test_hang_issue12364(self):
+        fs = [self.executor.submit(time.sleep, 0.1) for _ in range(50)]
+        self.executor.shutdown()
+        for f in fs:
+            f.result()
+
+
+class ThreadPoolShutdownTest(ThreadPoolMixin, ExecutorShutdownTest):
+    def _prime_executor(self):
+        pass
+
+    def test_threads_terminate(self):
+        self.executor.submit(mul, 21, 2)
+        self.executor.submit(mul, 6, 7)
+        self.executor.submit(mul, 3, 14)
+        self.assertEqual(len(self.executor._threads), 3)
+        self.executor.shutdown()
+        for t in self.executor._threads:
+            t.join()
+
+    def test_context_manager_shutdown(self):
+        with futures.ThreadPoolExecutor(max_workers=5) as e:
+            executor = e
+            self.assertEqual(list(e.map(abs, range(-5, 5))),
+                             [5, 4, 3, 2, 1, 0, 1, 2, 3, 4])
+
+        for t in executor._threads:
+            t.join()
+
+    def test_del_shutdown(self):
+        executor = futures.ThreadPoolExecutor(max_workers=5)
+        executor.map(abs, range(-5, 5))
+        threads = executor._threads
+        del executor
+        gc.collect()
+
+        for t in threads:
+            t.join()
+
+
+class ProcessPoolShutdownTest(ProcessPoolMixin, ExecutorShutdownTest):
+    def _prime_executor(self):
+        pass
+
+    def test_processes_terminate(self):
+        self.executor.submit(mul, 21, 2)
+        self.executor.submit(mul, 6, 7)
+        self.executor.submit(mul, 3, 14)
+        self.assertEqual(len(self.executor._processes), 5)
+        processes = self.executor._processes
+        self.executor.shutdown()
+
+        for p in processes:
+            p.join()
+
+    def test_context_manager_shutdown(self):
+        with futures.ProcessPoolExecutor(max_workers=5) as e:
+            processes = e._processes
+            self.assertEqual(list(e.map(abs, range(-5, 5))),
+                             [5, 4, 3, 2, 1, 0, 1, 2, 3, 4])
+
+        for p in processes:
+            p.join()
+
+    def test_del_shutdown(self):
+        executor = futures.ProcessPoolExecutor(max_workers=5)
+        list(executor.map(abs, range(-5, 5)))
+        queue_management_thread = executor._queue_management_thread
+        processes = executor._processes
+        del executor
+        gc.collect()
+
+        queue_management_thread.join()
+        for p in processes:
+            p.join()
+
+
+class WaitTests(unittest.TestCase):
+
+    def test_first_completed(self):
+        future1 = self.executor.submit(mul, 21, 2)
+        future2 = self.executor.submit(time.sleep, 1.5)
+
+        done, not_done = futures.wait(
+                [CANCELLED_FUTURE, future1, future2],
+                 return_when=futures.FIRST_COMPLETED)
+
+        self.assertEqual(set([future1]), done)
+        self.assertEqual(set([CANCELLED_FUTURE, future2]), not_done)
+
+    def test_first_completed_some_already_completed(self):
+        future1 = self.executor.submit(time.sleep, 1.5)
+
+        finished, pending = futures.wait(
+                 [CANCELLED_AND_NOTIFIED_FUTURE, SUCCESSFUL_FUTURE, future1],
+                 return_when=futures.FIRST_COMPLETED)
+
+        self.assertEqual(
+                set([CANCELLED_AND_NOTIFIED_FUTURE, SUCCESSFUL_FUTURE]),
+                finished)
+        self.assertEqual(set([future1]), pending)
+
+    def test_first_exception(self):
+        future1 = self.executor.submit(mul, 2, 21)
+        future2 = self.executor.submit(sleep_and_raise, 1.5)
+        future3 = self.executor.submit(time.sleep, 3)
+
+        finished, pending = futures.wait(
+                [future1, future2, future3],
+                return_when=futures.FIRST_EXCEPTION)
+
+        self.assertEqual(set([future1, future2]), finished)
+        self.assertEqual(set([future3]), pending)
+
+    def test_first_exception_some_already_complete(self):
+        future1 = self.executor.submit(divmod, 21, 0)
+        future2 = self.executor.submit(time.sleep, 1.5)
+
+        finished, pending = futures.wait(
+                [SUCCESSFUL_FUTURE,
+                 CANCELLED_FUTURE,
+                 CANCELLED_AND_NOTIFIED_FUTURE,
+                 future1, future2],
+                return_when=futures.FIRST_EXCEPTION)
+
+        self.assertEqual(set([SUCCESSFUL_FUTURE,
+                              CANCELLED_AND_NOTIFIED_FUTURE,
+                              future1]), finished)
+        self.assertEqual(set([CANCELLED_FUTURE, future2]), pending)
+
+    def test_first_exception_one_already_failed(self):
+        future1 = self.executor.submit(time.sleep, 2)
+
+        finished, pending = futures.wait(
+                 [EXCEPTION_FUTURE, future1],
+                 return_when=futures.FIRST_EXCEPTION)
+
+        self.assertEqual(set([EXCEPTION_FUTURE]), finished)
+        self.assertEqual(set([future1]), pending)
+
+    def test_all_completed(self):
+        future1 = self.executor.submit(divmod, 2, 0)
+        future2 = self.executor.submit(mul, 2, 21)
+
+        finished, pending = futures.wait(
+                [SUCCESSFUL_FUTURE,
+                 CANCELLED_AND_NOTIFIED_FUTURE,
+                 EXCEPTION_FUTURE,
+                 future1,
+                 future2],
+                return_when=futures.ALL_COMPLETED)
+
+        self.assertEqual(set([SUCCESSFUL_FUTURE,
+                              CANCELLED_AND_NOTIFIED_FUTURE,
+                              EXCEPTION_FUTURE,
+                              future1,
+                              future2]), finished)
+        self.assertEqual(set(), pending)
+
+    def test_timeout(self):
+        future1 = self.executor.submit(mul, 6, 7)
+        future2 = self.executor.submit(time.sleep, 3)
+
+        finished, pending = futures.wait(
+                [CANCELLED_AND_NOTIFIED_FUTURE,
+                 EXCEPTION_FUTURE,
+                 SUCCESSFUL_FUTURE,
+                 future1, future2],
+                timeout=1.5,
+                return_when=futures.ALL_COMPLETED)
+
+        self.assertEqual(set([CANCELLED_AND_NOTIFIED_FUTURE,
+                              EXCEPTION_FUTURE,
+                              SUCCESSFUL_FUTURE,
+                              future1]), finished)
+        self.assertEqual(set([future2]), pending)
+
+
+class ThreadPoolWaitTests(ThreadPoolMixin, WaitTests):
+
+    def test_pending_calls_race(self):
+        # Issue #14406: multi-threaded race condition when waiting on all
+        # futures.
+        event = threading.Event()
+        def future_func():
+            event.wait()
+        oldswitchinterval = sys.getcheckinterval()
+        sys.setcheckinterval(1)
+        try:
+            fs = set(self.executor.submit(future_func) for i in range(100))
+            event.set()
+            futures.wait(fs, return_when=futures.ALL_COMPLETED)
+        finally:
+            sys.setcheckinterval(oldswitchinterval)
+
+
+class ProcessPoolWaitTests(ProcessPoolMixin, WaitTests):
+    pass
+
+
+class AsCompletedTests(unittest.TestCase):
+    # TODO(brian@sweetapp.com): Should have a test with a non-zero timeout.
+    def test_no_timeout(self):
+        future1 = self.executor.submit(mul, 2, 21)
+        future2 = self.executor.submit(mul, 7, 6)
+
+        completed = set(futures.as_completed(
+                [CANCELLED_AND_NOTIFIED_FUTURE,
+                 EXCEPTION_FUTURE,
+                 SUCCESSFUL_FUTURE,
+                 future1, future2]))
+        self.assertEqual(set(
+                [CANCELLED_AND_NOTIFIED_FUTURE,
+                 EXCEPTION_FUTURE,
+                 SUCCESSFUL_FUTURE,
+                 future1, future2]),
+                completed)
+
+    def test_zero_timeout(self):
+        future1 = self.executor.submit(time.sleep, 2)
+        completed_futures = set()
+        try:
+            for future in futures.as_completed(
+                    [CANCELLED_AND_NOTIFIED_FUTURE,
+                     EXCEPTION_FUTURE,
+                     SUCCESSFUL_FUTURE,
+                     future1],
+                    timeout=0):
+                completed_futures.add(future)
+        except futures.TimeoutError:
+            pass
+
+        self.assertEqual(set([CANCELLED_AND_NOTIFIED_FUTURE,
+                              EXCEPTION_FUTURE,
+                              SUCCESSFUL_FUTURE]),
+                         completed_futures)
+
+    def test_duplicate_futures(self):
+        # Issue 20367. Duplicate futures should not raise exceptions or give
+        # duplicate responses.
+        future1 = self.executor.submit(time.sleep, 2)
+        completed = [f for f in futures.as_completed([future1,future1])]
+        self.assertEqual(len(completed), 1)
+
+
+class ThreadPoolAsCompletedTests(ThreadPoolMixin, AsCompletedTests):
+    pass
+
+
+class ProcessPoolAsCompletedTests(ProcessPoolMixin, AsCompletedTests):
+    pass
+
+
+class ExecutorTest(unittest.TestCase):
+    # Executor.shutdown() and context manager usage is tested by
+    # ExecutorShutdownTest.
+    def test_submit(self):
+        future = self.executor.submit(pow, 2, 8)
+        self.assertEqual(256, future.result())
+
+    def test_submit_keyword(self):
+        future = self.executor.submit(mul, 2, y=8)
+        self.assertEqual(16, future.result())
+
+    def test_map(self):
+        self.assertEqual(
+                list(self.executor.map(pow, range(10), range(10))),
+                list(map(pow, range(10), range(10))))
+
+    def test_map_exception(self):
+        i = self.executor.map(divmod, [1, 1, 1, 1], [2, 3, 0, 5])
+        self.assertEqual(next(i), (0, 1))
+        self.assertEqual(next(i), (0, 1))
+        self.assertRaises(ZeroDivisionError, next, i)
+
+    def test_map_timeout(self):
+        results = []
+        try:
+            for i in self.executor.map(time.sleep,
+                                       [0, 0, 3],
+                                       timeout=1.5):
+                results.append(i)
+        except futures.TimeoutError:
+            pass
+        else:
+            self.fail('expected TimeoutError')
+
+        self.assertEqual([None, None], results)
+
+
+class ThreadPoolExecutorTest(ThreadPoolMixin, ExecutorTest):
+    def test_map_submits_without_iteration(self):
+        """Tests verifying issue 11777."""
+        finished = []
+        def record_finished(n):
+            finished.append(n)
+
+        self.executor.map(record_finished, range(10))
+        self.executor.shutdown(wait=True)
+        self.assertEqual(len(finished), 10)
+
+
+class ProcessPoolExecutorTest(ProcessPoolMixin, ExecutorTest):
+    pass
+
+
+class FutureTests(unittest.TestCase):
+    def test_done_callback_with_result(self):
+        callback_result = [None]
+        def fn(callback_future):
+            callback_result[0] = callback_future.result()
+
+        f = Future()
+        f.add_done_callback(fn)
+        f.set_result(5)
+        self.assertEqual(5, callback_result[0])
+
+    def test_done_callback_with_exception(self):
+        callback_exception = [None]
+        def fn(callback_future):
+            callback_exception[0] = callback_future.exception()
+
+        f = Future()
+        f.add_done_callback(fn)
+        f.set_exception(Exception('test'))
+        self.assertEqual(('test',), callback_exception[0].args)
+
+    def test_done_callback_with_cancel(self):
+        was_cancelled = [None]
+        def fn(callback_future):
+            was_cancelled[0] = callback_future.cancelled()
+
+        f = Future()
+        f.add_done_callback(fn)
+        self.assertTrue(f.cancel())
+        self.assertTrue(was_cancelled[0])
+
+    def test_done_callback_raises(self):
+        with captured_stderr() as stderr:
+            raising_was_called = [False]
+            fn_was_called = [False]
+
+            def raising_fn(callback_future):
+                raising_was_called[0] = True
+                raise Exception('doh!')
+
+            def fn(callback_future):
+                fn_was_called[0] = True
+
+            f = Future()
+            f.add_done_callback(raising_fn)
+            f.add_done_callback(fn)
+            f.set_result(5)
+            self.assertTrue(raising_was_called)
+            self.assertTrue(fn_was_called)
+            self.assertIn('Exception: doh!', stderr.getvalue())
+
+    def test_done_callback_already_successful(self):
+        callback_result = [None]
+        def fn(callback_future):
+            callback_result[0] = callback_future.result()
+
+        f = Future()
+        f.set_result(5)
+        f.add_done_callback(fn)
+        self.assertEqual(5, callback_result[0])
+
+    def test_done_callback_already_failed(self):
+        callback_exception = [None]
+        def fn(callback_future):
+            callback_exception[0] = callback_future.exception()
+
+        f = Future()
+        f.set_exception(Exception('test'))
+        f.add_done_callback(fn)
+        self.assertEqual(('test',), callback_exception[0].args)
+
+    def test_done_callback_already_cancelled(self):
+        was_cancelled = [None]
+        def fn(callback_future):
+            was_cancelled[0] = callback_future.cancelled()
+
+        f = Future()
+        self.assertTrue(f.cancel())
+        f.add_done_callback(fn)
+        self.assertTrue(was_cancelled[0])
+
+    def test_repr(self):
+        self.assertRegexpMatches(repr(PENDING_FUTURE),
+                                 '<Future at 0x[0-9a-f]+L? state=pending>')
+        self.assertRegexpMatches(repr(RUNNING_FUTURE),
+                                 '<Future at 0x[0-9a-f]+L? state=running>')
+        self.assertRegexpMatches(repr(CANCELLED_FUTURE),
+                                 '<Future at 0x[0-9a-f]+L? state=cancelled>')
+        self.assertRegexpMatches(repr(CANCELLED_AND_NOTIFIED_FUTURE),
+                                 '<Future at 0x[0-9a-f]+L? state=cancelled>')
+        self.assertRegexpMatches(
+                repr(EXCEPTION_FUTURE),
+                '<Future at 0x[0-9a-f]+L? state=finished raised IOError>')
+        self.assertRegexpMatches(
+                repr(SUCCESSFUL_FUTURE),
+                '<Future at 0x[0-9a-f]+L? state=finished returned int>')
+
+    def test_cancel(self):
+        f1 = create_future(state=PENDING)
+        f2 = create_future(state=RUNNING)
+        f3 = create_future(state=CANCELLED)
+        f4 = create_future(state=CANCELLED_AND_NOTIFIED)
+        f5 = create_future(state=FINISHED, exception=IOError())
+        f6 = create_future(state=FINISHED, result=5)
+
+        self.assertTrue(f1.cancel())
+        self.assertEqual(f1._state, CANCELLED)
+
+        self.assertFalse(f2.cancel())
+        self.assertEqual(f2._state, RUNNING)
+
+        self.assertTrue(f3.cancel())
+        self.assertEqual(f3._state, CANCELLED)
+
+        self.assertTrue(f4.cancel())
+        self.assertEqual(f4._state, CANCELLED_AND_NOTIFIED)
+
+        self.assertFalse(f5.cancel())
+        self.assertEqual(f5._state, FINISHED)
+
+        self.assertFalse(f6.cancel())
+        self.assertEqual(f6._state, FINISHED)
+
+    def test_cancelled(self):
+        self.assertFalse(PENDING_FUTURE.cancelled())
+        self.assertFalse(RUNNING_FUTURE.cancelled())
+        self.assertTrue(CANCELLED_FUTURE.cancelled())
+        self.assertTrue(CANCELLED_AND_NOTIFIED_FUTURE.cancelled())
+        self.assertFalse(EXCEPTION_FUTURE.cancelled())
+        self.assertFalse(SUCCESSFUL_FUTURE.cancelled())
+
+    def test_done(self):
+        self.assertFalse(PENDING_FUTURE.done())
+        self.assertFalse(RUNNING_FUTURE.done())
+        self.assertTrue(CANCELLED_FUTURE.done())
+        self.assertTrue(CANCELLED_AND_NOTIFIED_FUTURE.done())
+        self.assertTrue(EXCEPTION_FUTURE.done())
+        self.assertTrue(SUCCESSFUL_FUTURE.done())
+
+    def test_running(self):
+        self.assertFalse(PENDING_FUTURE.running())
+        self.assertTrue(RUNNING_FUTURE.running())
+        self.assertFalse(CANCELLED_FUTURE.running())
+        self.assertFalse(CANCELLED_AND_NOTIFIED_FUTURE.running())
+        self.assertFalse(EXCEPTION_FUTURE.running())
+        self.assertFalse(SUCCESSFUL_FUTURE.running())
+
+    def test_result_with_timeout(self):
+        self.assertRaises(futures.TimeoutError,
+                          PENDING_FUTURE.result, timeout=0)
+        self.assertRaises(futures.TimeoutError,
+                          RUNNING_FUTURE.result, timeout=0)
+        self.assertRaises(futures.CancelledError,
+                          CANCELLED_FUTURE.result, timeout=0)
+        self.assertRaises(futures.CancelledError,
+                          CANCELLED_AND_NOTIFIED_FUTURE.result, timeout=0)
+        self.assertRaises(IOError, EXCEPTION_FUTURE.result, timeout=0)
+        self.assertEqual(SUCCESSFUL_FUTURE.result(timeout=0), 42)
+
+    def test_result_with_success(self):
+        # TODO(brian@sweetapp.com): This test is timing dependant.
+        def notification():
+            # Wait until the main thread is waiting for the result.
+            time.sleep(1)
+            f1.set_result(42)
+
+        f1 = create_future(state=PENDING)
+        t = threading.Thread(target=notification)
+        t.start()
+
+        self.assertEqual(f1.result(timeout=5), 42)
+
+    def test_result_with_cancel(self):
+        # TODO(brian@sweetapp.com): This test is timing dependant.
+        def notification():
+            # Wait until the main thread is waiting for the result.
+            time.sleep(1)
+            f1.cancel()
+
+        f1 = create_future(state=PENDING)
+        t = threading.Thread(target=notification)
+        t.start()
+
+        self.assertRaises(futures.CancelledError, f1.result, timeout=5)
+
+    def test_exception_with_timeout(self):
+        self.assertRaises(futures.TimeoutError,
+                          PENDING_FUTURE.exception, timeout=0)
+        self.assertRaises(futures.TimeoutError,
+                          RUNNING_FUTURE.exception, timeout=0)
+        self.assertRaises(futures.CancelledError,
+                          CANCELLED_FUTURE.exception, timeout=0)
+        self.assertRaises(futures.CancelledError,
+                          CANCELLED_AND_NOTIFIED_FUTURE.exception, timeout=0)
+        self.assertTrue(isinstance(EXCEPTION_FUTURE.exception(timeout=0),
+                                   IOError))
+        self.assertEqual(SUCCESSFUL_FUTURE.exception(timeout=0), None)
+
+    def test_exception_with_success(self):
+        def notification():
+            # Wait until the main thread is waiting for the exception.
+            time.sleep(1)
+            with f1._condition:
+                f1._state = FINISHED
+                f1._exception = IOError()
+                f1._condition.notify_all()
+
+        f1 = create_future(state=PENDING)
+        t = threading.Thread(target=notification)
+        t.start()
+
+        self.assertTrue(isinstance(f1.exception(timeout=5), IOError))
+
+@reap_threads
+def test_main():
+    try:
+        test_support.run_unittest(ProcessPoolExecutorTest,
+                                  ThreadPoolExecutorTest,
+                                  ProcessPoolWaitTests,
+                                  ThreadPoolWaitTests,
+                                  ProcessPoolAsCompletedTests,
+                                  ThreadPoolAsCompletedTests,
+                                  FutureTests,
+                                  ProcessPoolShutdownTest,
+                                  ThreadPoolShutdownTest)
+    finally:
+        test_support.reap_children()
+
+if __name__ == "__main__":
+    test_main()