1 files changed, 838 insertions, 0 deletions
diff --git a/Lib/test/test_asyncio/test_locks.py b/Lib/test/test_asyncio/test_locks.py
new file mode 100644
index 0000000000..df106e0d15
--- /dev/null
+++ b/Lib/test/test_asyncio/test_locks.py
@@ -0,0 +1,838 @@
+"""Tests for lock.py"""
+
+import unittest
+import unittest.mock
+import re
+
+from asyncio import events
+from asyncio import futures
+from asyncio import locks
+from asyncio import tasks
+from asyncio import test_utils
+
+
+STR_RGX_REPR = (
+    r'^<(?P<class>.*?) object at (?P<address>.*?)'
+    r'\[(?P<extras>'
+    r'(set|unset|locked|unlocked)(,value:\d)?(,waiters:\d+)?'
+    r')\]>\Z'
+)
+RGX_REPR = re.compile(STR_RGX_REPR)
+
+
+class LockTests(unittest.TestCase):
+
+    def setUp(self):
+        self.loop = test_utils.TestLoop()
+        events.set_event_loop(None)
+
+    def tearDown(self):
+        self.loop.close()
+
+    def test_ctor_loop(self):
+        loop = unittest.mock.Mock()
+        lock = locks.Lock(loop=loop)
+        self.assertIs(lock._loop, loop)
+
+        lock = locks.Lock(loop=self.loop)
+        self.assertIs(lock._loop, self.loop)
+
+    def test_ctor_noloop(self):
+        try:
+            events.set_event_loop(self.loop)
+            lock = locks.Lock()
+            self.assertIs(lock._loop, self.loop)
+        finally:
+            events.set_event_loop(None)
+
+    def test_repr(self):
+        lock = locks.Lock(loop=self.loop)
+        self.assertTrue(repr(lock).endswith('[unlocked]>'))
+        self.assertTrue(RGX_REPR.match(repr(lock)))
+
+        @tasks.coroutine
+        def acquire_lock():
+            yield from lock
+
+        self.loop.run_until_complete(acquire_lock())
+        self.assertTrue(repr(lock).endswith('[locked]>'))
+        self.assertTrue(RGX_REPR.match(repr(lock)))
+
+    def test_lock(self):
+        lock = locks.Lock(loop=self.loop)
+
+        @tasks.coroutine
+        def acquire_lock():
+            return (yield from lock)
+
+        res = self.loop.run_until_complete(acquire_lock())
+
+        self.assertTrue(res)
+        self.assertTrue(lock.locked())
+
+        lock.release()
+        self.assertFalse(lock.locked())
+
+    def test_acquire(self):
+        lock = locks.Lock(loop=self.loop)
+        result = []
+
+        self.assertTrue(self.loop.run_until_complete(lock.acquire()))
+
+        @tasks.coroutine
+        def c1(result):
+            if (yield from lock.acquire()):
+                result.append(1)
+            return True
+
+        @tasks.coroutine
+        def c2(result):
+            if (yield from lock.acquire()):
+                result.append(2)
+            return True
+
+        @tasks.coroutine
+        def c3(result):
+            if (yield from lock.acquire()):
+                result.append(3)
+            return True
+
+        t1 = tasks.Task(c1(result), loop=self.loop)
+        t2 = tasks.Task(c2(result), loop=self.loop)
+
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([], result)
+
+        lock.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1], result)
+
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1], result)
+
+        t3 = tasks.Task(c3(result), loop=self.loop)
+
+        lock.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1, 2], result)
+
+        lock.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1, 2, 3], result)
+
+        self.assertTrue(t1.done())
+        self.assertTrue(t1.result())
+        self.assertTrue(t2.done())
+        self.assertTrue(t2.result())
+        self.assertTrue(t3.done())
+        self.assertTrue(t3.result())
+
+    def test_acquire_cancel(self):
+        lock = locks.Lock(loop=self.loop)
+        self.assertTrue(self.loop.run_until_complete(lock.acquire()))
+
+        task = tasks.Task(lock.acquire(), loop=self.loop)
+        self.loop.call_soon(task.cancel)
+        self.assertRaises(
+            futures.CancelledError,
+            self.loop.run_until_complete, task)
+        self.assertFalse(lock._waiters)
+
+    def test_cancel_race(self):
+        # Several tasks:
+        # - A acquires the lock
+        # - B is blocked in aqcuire()
+        # - C is blocked in aqcuire()
+        #
+        # Now, concurrently:
+        # - B is cancelled
+        # - A releases the lock
+        #
+        # If B's waiter is marked cancelled but not yet removed from
+        # _waiters, A's release() call will crash when trying to set
+        # B's waiter; instead, it should move on to C's waiter.
+
+        # Setup: A has the lock, b and c are waiting.
+        lock = locks.Lock(loop=self.loop)
+
+        @tasks.coroutine
+        def lockit(name, blocker):
+            yield from lock.acquire()
+            try:
+                if blocker is not None:
+                    yield from blocker
+            finally:
+                lock.release()
+
+        fa = futures.Future(loop=self.loop)
+        ta = tasks.Task(lockit('A', fa), loop=self.loop)
+        test_utils.run_briefly(self.loop)
+        self.assertTrue(lock.locked())
+        tb = tasks.Task(lockit('B', None), loop=self.loop)
+        test_utils.run_briefly(self.loop)
+        self.assertEqual(len(lock._waiters), 1)
+        tc = tasks.Task(lockit('C', None), loop=self.loop)
+        test_utils.run_briefly(self.loop)
+        self.assertEqual(len(lock._waiters), 2)
+
+        # Create the race and check.
+        # Without the fix this failed at the last assert.
+        fa.set_result(None)
+        tb.cancel()
+        self.assertTrue(lock._waiters[0].cancelled())
+        test_utils.run_briefly(self.loop)
+        self.assertFalse(lock.locked())
+        self.assertTrue(ta.done())
+        self.assertTrue(tb.cancelled())
+        self.assertTrue(tc.done())
+
+    def test_release_not_acquired(self):
+        lock = locks.Lock(loop=self.loop)
+
+        self.assertRaises(RuntimeError, lock.release)
+
+    def test_release_no_waiters(self):
+        lock = locks.Lock(loop=self.loop)
+        self.loop.run_until_complete(lock.acquire())
+        self.assertTrue(lock.locked())
+
+        lock.release()
+        self.assertFalse(lock.locked())
+
+    def test_context_manager(self):
+        lock = locks.Lock(loop=self.loop)
+
+        @tasks.coroutine
+        def acquire_lock():
+            return (yield from lock)
+
+        with self.loop.run_until_complete(acquire_lock()):
+            self.assertTrue(lock.locked())
+
+        self.assertFalse(lock.locked())
+
+    def test_context_manager_no_yield(self):
+        lock = locks.Lock(loop=self.loop)
+
+        try:
+            with lock:
+                self.fail('RuntimeError is not raised in with expression')
+        except RuntimeError as err:
+            self.assertEqual(
+                str(err),
+                '"yield from" should be used as context manager expression')
+
+
+class EventTests(unittest.TestCase):
+
+    def setUp(self):
+        self.loop = test_utils.TestLoop()
+        events.set_event_loop(None)
+
+    def tearDown(self):
+        self.loop.close()
+
+    def test_ctor_loop(self):
+        loop = unittest.mock.Mock()
+        ev = locks.Event(loop=loop)
+        self.assertIs(ev._loop, loop)
+
+        ev = locks.Event(loop=self.loop)
+        self.assertIs(ev._loop, self.loop)
+
+    def test_ctor_noloop(self):
+        try:
+            events.set_event_loop(self.loop)
+            ev = locks.Event()
+            self.assertIs(ev._loop, self.loop)
+        finally:
+            events.set_event_loop(None)
+
+    def test_repr(self):
+        ev = locks.Event(loop=self.loop)
+        self.assertTrue(repr(ev).endswith('[unset]>'))
+        match = RGX_REPR.match(repr(ev))
+        self.assertEqual(match.group('extras'), 'unset')
+
+        ev.set()
+        self.assertTrue(repr(ev).endswith('[set]>'))
+        self.assertTrue(RGX_REPR.match(repr(ev)))
+
+        ev._waiters.append(unittest.mock.Mock())
+        self.assertTrue('waiters:1' in repr(ev))
+        self.assertTrue(RGX_REPR.match(repr(ev)))
+
+    def test_wait(self):
+        ev = locks.Event(loop=self.loop)
+        self.assertFalse(ev.is_set())
+
+        result = []
+
+        @tasks.coroutine
+        def c1(result):
+            if (yield from ev.wait()):
+                result.append(1)
+
+        @tasks.coroutine
+        def c2(result):
+            if (yield from ev.wait()):
+                result.append(2)
+
+        @tasks.coroutine
+        def c3(result):
+            if (yield from ev.wait()):
+                result.append(3)
+
+        t1 = tasks.Task(c1(result), loop=self.loop)
+        t2 = tasks.Task(c2(result), loop=self.loop)
+
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([], result)
+
+        t3 = tasks.Task(c3(result), loop=self.loop)
+
+        ev.set()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([3, 1, 2], result)
+
+        self.assertTrue(t1.done())
+        self.assertIsNone(t1.result())
+        self.assertTrue(t2.done())
+        self.assertIsNone(t2.result())
+        self.assertTrue(t3.done())
+        self.assertIsNone(t3.result())
+
+    def test_wait_on_set(self):
+        ev = locks.Event(loop=self.loop)
+        ev.set()
+
+        res = self.loop.run_until_complete(ev.wait())
+        self.assertTrue(res)
+
+    def test_wait_cancel(self):
+        ev = locks.Event(loop=self.loop)
+
+        wait = tasks.Task(ev.wait(), loop=self.loop)
+        self.loop.call_soon(wait.cancel)
+        self.assertRaises(
+            futures.CancelledError,
+            self.loop.run_until_complete, wait)
+        self.assertFalse(ev._waiters)
+
+    def test_clear(self):
+        ev = locks.Event(loop=self.loop)
+        self.assertFalse(ev.is_set())
+
+        ev.set()
+        self.assertTrue(ev.is_set())
+
+        ev.clear()
+        self.assertFalse(ev.is_set())
+
+    def test_clear_with_waiters(self):
+        ev = locks.Event(loop=self.loop)
+        result = []
+
+        @tasks.coroutine
+        def c1(result):
+            if (yield from ev.wait()):
+                result.append(1)
+            return True
+
+        t = tasks.Task(c1(result), loop=self.loop)
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([], result)
+
+        ev.set()
+        ev.clear()
+        self.assertFalse(ev.is_set())
+
+        ev.set()
+        ev.set()
+        self.assertEqual(1, len(ev._waiters))
+
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1], result)
+        self.assertEqual(0, len(ev._waiters))
+
+        self.assertTrue(t.done())
+        self.assertTrue(t.result())
+
+
+class ConditionTests(unittest.TestCase):
+
+    def setUp(self):
+        self.loop = test_utils.TestLoop()
+        events.set_event_loop(None)
+
+    def tearDown(self):
+        self.loop.close()
+
+    def test_ctor_loop(self):
+        loop = unittest.mock.Mock()
+        cond = locks.Condition(loop=loop)
+        self.assertIs(cond._loop, loop)
+
+        cond = locks.Condition(loop=self.loop)
+        self.assertIs(cond._loop, self.loop)
+
+    def test_ctor_noloop(self):
+        try:
+            events.set_event_loop(self.loop)
+            cond = locks.Condition()
+            self.assertIs(cond._loop, self.loop)
+        finally:
+            events.set_event_loop(None)
+
+    def test_wait(self):
+        cond = locks.Condition(loop=self.loop)
+        result = []
+
+        @tasks.coroutine
+        def c1(result):
+            yield from cond.acquire()
+            if (yield from cond.wait()):
+                result.append(1)
+            return True
+
+        @tasks.coroutine
+        def c2(result):
+            yield from cond.acquire()
+            if (yield from cond.wait()):
+                result.append(2)
+            return True
+
+        @tasks.coroutine
+        def c3(result):
+            yield from cond.acquire()
+            if (yield from cond.wait()):
+                result.append(3)
+            return True
+
+        t1 = tasks.Task(c1(result), loop=self.loop)
+        t2 = tasks.Task(c2(result), loop=self.loop)
+        t3 = tasks.Task(c3(result), loop=self.loop)
+
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([], result)
+        self.assertFalse(cond.locked())
+
+        self.assertTrue(self.loop.run_until_complete(cond.acquire()))
+        cond.notify()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([], result)
+        self.assertTrue(cond.locked())
+
+        cond.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1], result)
+        self.assertTrue(cond.locked())
+
+        cond.notify(2)
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1], result)
+        self.assertTrue(cond.locked())
+
+        cond.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1, 2], result)
+        self.assertTrue(cond.locked())
+
+        cond.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1, 2, 3], result)
+        self.assertTrue(cond.locked())
+
+        self.assertTrue(t1.done())
+        self.assertTrue(t1.result())
+        self.assertTrue(t2.done())
+        self.assertTrue(t2.result())
+        self.assertTrue(t3.done())
+        self.assertTrue(t3.result())
+
+    def test_wait_cancel(self):
+        cond = locks.Condition(loop=self.loop)
+        self.loop.run_until_complete(cond.acquire())
+
+        wait = tasks.Task(cond.wait(), loop=self.loop)
+        self.loop.call_soon(wait.cancel)
+        self.assertRaises(
+            futures.CancelledError,
+            self.loop.run_until_complete, wait)
+        self.assertFalse(cond._waiters)
+        self.assertTrue(cond.locked())
+
+    def test_wait_unacquired(self):
+        cond = locks.Condition(loop=self.loop)
+        self.assertRaises(
+            RuntimeError,
+            self.loop.run_until_complete, cond.wait())
+
+    def test_wait_for(self):
+        cond = locks.Condition(loop=self.loop)
+        presult = False
+
+        def predicate():
+            return presult
+
+        result = []
+
+        @tasks.coroutine
+        def c1(result):
+            yield from cond.acquire()
+            if (yield from cond.wait_for(predicate)):
+                result.append(1)
+                cond.release()
+            return True
+
+        t = tasks.Task(c1(result), loop=self.loop)
+
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([], result)
+
+        self.loop.run_until_complete(cond.acquire())
+        cond.notify()
+        cond.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([], result)
+
+        presult = True
+        self.loop.run_until_complete(cond.acquire())
+        cond.notify()
+        cond.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1], result)
+
+        self.assertTrue(t.done())
+        self.assertTrue(t.result())
+
+    def test_wait_for_unacquired(self):
+        cond = locks.Condition(loop=self.loop)
+
+        # predicate can return true immediately
+        res = self.loop.run_until_complete(cond.wait_for(lambda: [1, 2, 3]))
+        self.assertEqual([1, 2, 3], res)
+
+        self.assertRaises(
+            RuntimeError,
+            self.loop.run_until_complete,
+            cond.wait_for(lambda: False))
+
+    def test_notify(self):
+        cond = locks.Condition(loop=self.loop)
+        result = []
+
+        @tasks.coroutine
+        def c1(result):
+            yield from cond.acquire()
+            if (yield from cond.wait()):
+                result.append(1)
+                cond.release()
+            return True
+
+        @tasks.coroutine
+        def c2(result):
+            yield from cond.acquire()
+            if (yield from cond.wait()):
+                result.append(2)
+                cond.release()
+            return True
+
+        @tasks.coroutine
+        def c3(result):
+            yield from cond.acquire()
+            if (yield from cond.wait()):
+                result.append(3)
+                cond.release()
+            return True
+
+        t1 = tasks.Task(c1(result), loop=self.loop)
+        t2 = tasks.Task(c2(result), loop=self.loop)
+        t3 = tasks.Task(c3(result), loop=self.loop)
+
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([], result)
+
+        self.loop.run_until_complete(cond.acquire())
+        cond.notify(1)
+        cond.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1], result)
+
+        self.loop.run_until_complete(cond.acquire())
+        cond.notify(1)
+        cond.notify(2048)
+        cond.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1, 2, 3], result)
+
+        self.assertTrue(t1.done())
+        self.assertTrue(t1.result())
+        self.assertTrue(t2.done())
+        self.assertTrue(t2.result())
+        self.assertTrue(t3.done())
+        self.assertTrue(t3.result())
+
+    def test_notify_all(self):
+        cond = locks.Condition(loop=self.loop)
+
+        result = []
+
+        @tasks.coroutine
+        def c1(result):
+            yield from cond.acquire()
+            if (yield from cond.wait()):
+                result.append(1)
+                cond.release()
+            return True
+
+        @tasks.coroutine
+        def c2(result):
+            yield from cond.acquire()
+            if (yield from cond.wait()):
+                result.append(2)
+                cond.release()
+            return True
+
+        t1 = tasks.Task(c1(result), loop=self.loop)
+        t2 = tasks.Task(c2(result), loop=self.loop)
+
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([], result)
+
+        self.loop.run_until_complete(cond.acquire())
+        cond.notify_all()
+        cond.release()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1, 2], result)
+
+        self.assertTrue(t1.done())
+        self.assertTrue(t1.result())
+        self.assertTrue(t2.done())
+        self.assertTrue(t2.result())
+
+    def test_notify_unacquired(self):
+        cond = locks.Condition(loop=self.loop)
+        self.assertRaises(RuntimeError, cond.notify)
+
+    def test_notify_all_unacquired(self):
+        cond = locks.Condition(loop=self.loop)
+        self.assertRaises(RuntimeError, cond.notify_all)
+
+    def test_repr(self):
+        cond = locks.Condition(loop=self.loop)
+        self.assertTrue('unlocked' in repr(cond))
+        self.assertTrue(RGX_REPR.match(repr(cond)))
+
+        self.loop.run_until_complete(cond.acquire())
+        self.assertTrue('locked' in repr(cond))
+
+        cond._waiters.append(unittest.mock.Mock())
+        self.assertTrue('waiters:1' in repr(cond))
+        self.assertTrue(RGX_REPR.match(repr(cond)))
+
+        cond._waiters.append(unittest.mock.Mock())
+        self.assertTrue('waiters:2' in repr(cond))
+        self.assertTrue(RGX_REPR.match(repr(cond)))
+
+    def test_context_manager(self):
+        cond = locks.Condition(loop=self.loop)
+
+        @tasks.coroutine
+        def acquire_cond():
+            return (yield from cond)
+
+        with self.loop.run_until_complete(acquire_cond()):
+            self.assertTrue(cond.locked())
+
+        self.assertFalse(cond.locked())
+
+    def test_context_manager_no_yield(self):
+        cond = locks.Condition(loop=self.loop)
+
+        try:
+            with cond:
+                self.fail('RuntimeError is not raised in with expression')
+        except RuntimeError as err:
+            self.assertEqual(
+                str(err),
+                '"yield from" should be used as context manager expression')
+
+
+class SemaphoreTests(unittest.TestCase):
+
+    def setUp(self):
+        self.loop = test_utils.TestLoop()
+        events.set_event_loop(None)
+
+    def tearDown(self):
+        self.loop.close()
+
+    def test_ctor_loop(self):
+        loop = unittest.mock.Mock()
+        sem = locks.Semaphore(loop=loop)
+        self.assertIs(sem._loop, loop)
+
+        sem = locks.Semaphore(loop=self.loop)
+        self.assertIs(sem._loop, self.loop)
+
+    def test_ctor_noloop(self):
+        try:
+            events.set_event_loop(self.loop)
+            sem = locks.Semaphore()
+            self.assertIs(sem._loop, self.loop)
+        finally:
+            events.set_event_loop(None)
+
+    def test_initial_value_zero(self):
+        sem = locks.Semaphore(0, loop=self.loop)
+        self.assertTrue(sem.locked())
+
+    def test_repr(self):
+        sem = locks.Semaphore(loop=self.loop)
+        self.assertTrue(repr(sem).endswith('[unlocked,value:1]>'))
+        self.assertTrue(RGX_REPR.match(repr(sem)))
+
+        self.loop.run_until_complete(sem.acquire())
+        self.assertTrue(repr(sem).endswith('[locked]>'))
+        self.assertTrue('waiters' not in repr(sem))
+        self.assertTrue(RGX_REPR.match(repr(sem)))
+
+        sem._waiters.append(unittest.mock.Mock())
+        self.assertTrue('waiters:1' in repr(sem))
+        self.assertTrue(RGX_REPR.match(repr(sem)))
+
+        sem._waiters.append(unittest.mock.Mock())
+        self.assertTrue('waiters:2' in repr(sem))
+        self.assertTrue(RGX_REPR.match(repr(sem)))
+
+    def test_semaphore(self):
+        sem = locks.Semaphore(loop=self.loop)
+        self.assertEqual(1, sem._value)
+
+        @tasks.coroutine
+        def acquire_lock():
+            return (yield from sem)
+
+        res = self.loop.run_until_complete(acquire_lock())
+
+        self.assertTrue(res)
+        self.assertTrue(sem.locked())
+        self.assertEqual(0, sem._value)
+
+        sem.release()
+        self.assertFalse(sem.locked())
+        self.assertEqual(1, sem._value)
+
+    def test_semaphore_value(self):
+        self.assertRaises(ValueError, locks.Semaphore, -1)
+
+    def test_acquire(self):
+        sem = locks.Semaphore(3, loop=self.loop)
+        result = []
+
+        self.assertTrue(self.loop.run_until_complete(sem.acquire()))
+        self.assertTrue(self.loop.run_until_complete(sem.acquire()))
+        self.assertFalse(sem.locked())
+
+        @tasks.coroutine
+        def c1(result):
+            yield from sem.acquire()
+            result.append(1)
+            return True
+
+        @tasks.coroutine
+        def c2(result):
+            yield from sem.acquire()
+            result.append(2)
+            return True
+
+        @tasks.coroutine
+        def c3(result):
+            yield from sem.acquire()
+            result.append(3)
+            return True
+
+        @tasks.coroutine
+        def c4(result):
+            yield from sem.acquire()
+            result.append(4)
+            return True
+
+        t1 = tasks.Task(c1(result), loop=self.loop)
+        t2 = tasks.Task(c2(result), loop=self.loop)
+        t3 = tasks.Task(c3(result), loop=self.loop)
+
+        test_utils.run_briefly(self.loop)
+        self.assertEqual([1], result)
+        self.assertTrue(sem.locked())
+        self.assertEqual(2, len(sem._waiters))
+        self.assertEqual(0, sem._value)
+
+        t4 = tasks.Task(c4(result), loop=self.loop)
+
+        sem.release()
+        sem.release()
+        self.assertEqual(2, sem._value)
+
+        test_utils.run_briefly(self.loop)
+        self.assertEqual(0, sem._value)
+        self.assertEqual([1, 2, 3], result)
+        self.assertTrue(sem.locked())
+        self.assertEqual(1, len(sem._waiters))
+        self.assertEqual(0, sem._value)
+
+        self.assertTrue(t1.done())
+        self.assertTrue(t1.result())
+        self.assertTrue(t2.done())
+        self.assertTrue(t2.result())
+        self.assertTrue(t3.done())
+        self.assertTrue(t3.result())
+        self.assertFalse(t4.done())
+
+        # cleanup locked semaphore
+        sem.release()
+
+    def test_acquire_cancel(self):
+        sem = locks.Semaphore(loop=self.loop)
+        self.loop.run_until_complete(sem.acquire())
+
+        acquire = tasks.Task(sem.acquire(), loop=self.loop)
+        self.loop.call_soon(acquire.cancel)
+        self.assertRaises(
+            futures.CancelledError,
+            self.loop.run_until_complete, acquire)
+        self.assertFalse(sem._waiters)
+
+    def test_release_not_acquired(self):
+        sem = locks.BoundedSemaphore(loop=self.loop)
+
+        self.assertRaises(ValueError, sem.release)
+
+    def test_release_no_waiters(self):
+        sem = locks.Semaphore(loop=self.loop)
+        self.loop.run_until_complete(sem.acquire())
+        self.assertTrue(sem.locked())
+
+        sem.release()
+        self.assertFalse(sem.locked())
+
+    def test_context_manager(self):
+        sem = locks.Semaphore(2, loop=self.loop)
+
+        @tasks.coroutine
+        def acquire_lock():
+            return (yield from sem)
+
+        with self.loop.run_until_complete(acquire_lock()):
+            self.assertFalse(sem.locked())
+            self.assertEqual(1, sem._value)
+
+            with self.loop.run_until_complete(acquire_lock()):
+                self.assertTrue(sem.locked())
+
+        self.assertEqual(2, sem._value)
+
+
+if __name__ == '__main__':
+    unittest.main()