Add a dialplan timeout test

Verify that when a session is parked but not handled within the timeout
period (in this case 3 seconds as set in our CI dialplan) it is cancelled
by FS. In the contrary case verify that a simple `session.answer()` within
the timeout results in a successful SIPp `uac` client scenario.

Resolves #47

tests/test_coroutines.py

@@ -88,3 +88,39 @@ async def timeout_on_hangup(self, sess):
         assert task.done()
         with pytest.raises(asyncio.TimeoutError):
             task.result()
+
+
+@pytest.mark.parametrize('sleep', [2, 5])
+def test_simplest_flow(fssock, scenario, client, ael, sleep):
+    """Verify that a coroutine can satisfy SIPp's simplest call flow.
+
+    Additionally, verify that when calls are not answered and left in the park
+    state they time out and are rejected after 3 seconds (according to the CI
+    dialplan).
+    """
+    class MyApp:
+        @coroutine("CHANNEL_PARK")
+        async def answer_pause_hangup(self, sess):
+            await asyncio.sleep(sleep)
+            sess.answer()
+            await sess.recv("CHANNEL_HANGUP")
+
+
+    client.connect()
+    client.listener = ael
+    # assigning a listener overrides it's call lookup var so restore it
+    client.listener.call_tracking_header = 'variable_call_uuid'
+    assert 'default' == client.load_app(MyApp, on_value="default")
+
+    uac = scenario.prepare()[1]
+    uac.proxyaddr = None
+    uac.destaddr = fssock
+
+    # make the call
+    if sleep > 3:
+        # XML dialplan's `park_timeout` should reject the call
+        with pytest.raises(RuntimeError):
+            uac()
+    else:
+        # call should be hung up by this UAC
+        uac()