More tests of Semaphore, timeout, and with-statement.

tornado/test/locks_test.py

@@ -296,11 +296,23 @@ def test_context_manager_exception(self):
 
     @gen_test
     def test_context_manager_timeout(self):
+        sem = locks.Semaphore()
+        with (yield sem.acquire(timedelta(seconds=0.01))):
+            pass
+
+        # Semaphore was released and can be acquired again.
+        self.assertTrue(sem.acquire().done())
+
+    @gen_test
+    def test_context_manager_timeout_error(self):
         sem = locks.Semaphore(value=0)
         with self.assertRaises(gen.TimeoutError):
             with (yield sem.acquire(timedelta(seconds=0.01))):
                 pass
 
+        # Counter is still 0.
+        self.assertFalse(sem.acquire().done())
+
     @gen_test
     def test_context_manager_contended(self):
         sem = locks.Semaphore()