add ssdp device discovery test

tests/test_ssdp.py

@@ -0,0 +1,45 @@
+from twisted.internet import reactor, defer
+from twisted.trial import unittest
+from txupnp.constants import SSDP_PORT
+from txupnp import mocks
+from txupnp.ssdp import SSDPFactory
+
+
+class TestDiscoverGateway(unittest.TestCase):
+    router_address = '10.0.0.1'
+    client_address = '10.0.0.10'
+    service_name = 'WANCommonInterfaceConfig:1'
+    st = 'urn:schemas-upnp-org:service:%s' % service_name
+    port = 49152
+    location = 'InternetGatewayDevice.xml'
+    usn = 'uuid:00000000-0000-0000-0000-000000000000::%s' % st
+    version = 'Linux, UPnP/1.0, DIR-890L Ver 1.20'
+
+    expected_devices = [
+        {
+            'cache_control': 'max-age=1800',
+            'location': 'http://%s:%i/%s' % (router_address, port, location),
+            'server': version,
+            'st': st,
+            'usn': usn
+         }
+    ]
+
+    def setUp(self):
+        fake_reactor = mocks.MockReactor()
+        reactor.listenMulticast = fake_reactor.listenMulticast
+        self.reactor = reactor
+        server_protocol = mocks.MockSSDPServiceGatewayProtocol(
+            self.router_address, self.service_name, self.st, self.port, self.location, self.usn, self.version
+        )
+        self.server_port = self.reactor.listenMulticast(SSDP_PORT, server_protocol)
+
+    def tearDown(self):
+        self.server_port.stopListening()
+
+    @defer.inlineCallbacks
+    def test_discover(self):
+        client_factory = SSDPFactory(self.reactor, self.client_address, self.router_address)
+        result = yield client_factory.m_search(self.router_address)
+        self.assertListEqual(self.expected_devices, result)
+        client_factory.disconnect()