Make test pass with fake ring rpc

tests/test_ring.py

@@ -1,16 +1,40 @@
 import unittest
+import concurrent.futures.thread
 
 import dispatch
-import ring.task.v1.service_pb2
+import ring.task.v1.service_pb2 as service_pb
+import ring.task.v1.service_pb2_grpc as service_grpc
 import dispatch.http.v1.http_pb2
 import grpc
 import google.protobuf.any_pb2
 
 
+class FakeRing(service_grpc.ServiceServicer):
+    def CreateTasks(self, request, context):
+        return service_pb.CreateTasksResponse()
+
+
 class TestRing(unittest.TestCase):
+    def setUp(self):
+        self.thread_pool = concurrent.futures.thread.ThreadPoolExecutor()
+        self.server = grpc.server(self.thread_pool)
+
+        port = self.server.add_insecure_port("127.0.0.1:0")
+
+        servicer = FakeRing()
+
+        service_grpc.add_ServiceServicer_to_server(servicer, self.server)
+        self.server.start()
+
+        channel = grpc.insecure_channel(f"127.0.0.1:{port}")
+        self.ring_stub = service_grpc.ServiceStub(channel)
+
+    def tearDown(self):
+        self.server.stop(0)
+        self.server.wait_for_termination()
+        self.thread_pool.shutdown(wait=True, cancel_futures=True)
+
     def test_ring(self):
-        channel = grpc.insecure_channel("localhost:4001")
-        stub = ring.task.v1.service_pb2_grpc.ServiceStub(channel)
 
         request = dispatch.http.v1.http_pb2.Request(
             url="https://www.google.com", method="GET"
@@ -19,9 +43,9 @@ def test_ring(self):
         input = google.protobuf.any_pb2.Any()
         input.Pack(request)
 
-        create_task_input = ring.task.v1.service_pb2.CreateTaskInput(
+        create_task_input = service_pb.CreateTaskInput(
             coroutine_uri="arn:aws:lambda:us-west-2:012345678912:function:dispatch-http",
             input=input,
         )
-        req = ring.task.v1.service_pb2.CreateTasksRequest(tasks=[create_task_input])
-        resp = stub.CreateTasks(req)
+        req = service_pb.CreateTasksRequest(tasks=[create_task_input])
+        resp = self.ring_stub.CreateTasks(req)