implement unimplemented_method interop test

src/csharp/Grpc.Core/Internal/ServerCallHandler.cs

@@ -284,7 +284,7 @@ namespace Grpc.Core.Internal
             var finishedTask = asyncCall.ServerSideCallAsync();
             var responseStream = new ServerResponseStream<byte[], byte[]>(asyncCall);
 
-            await responseStream.WriteStatusAsync(new Status(StatusCode.Unimplemented, "No such method."), Metadata.Empty).ConfigureAwait(false);
+            await responseStream.WriteStatusAsync(new Status(StatusCode.Unimplemented, ""), Metadata.Empty).ConfigureAwait(false);
             await finishedTask.ConfigureAwait(false);
         }
     }

src/csharp/Grpc.IntegrationTesting/InteropClient.cs

@@ -131,8 +131,7 @@ namespace Grpc.IntegrationTesting
                 };
             }
             var channel = new Channel(options.ServerHost, options.ServerPort, credentials, channelOptions);
-            TestService.TestServiceClient client = new TestService.TestServiceClient(channel);
-            await RunTestCaseAsync(client, options);
+            await RunTestCaseAsync(channel, options);
             await channel.ShutdownAsync();
         }
 
@@ -160,8 +159,9 @@ namespace Grpc.IntegrationTesting
             return credentials;
         }
 
-        private async Task RunTestCaseAsync(TestService.TestServiceClient client, ClientOptions options)
+        private async Task RunTestCaseAsync(Channel channel, ClientOptions options)
         {
+            var client = new TestService.TestServiceClient(channel);
             switch (options.TestCase)
             {
                 case "empty_unary":
@@ -209,6 +209,9 @@ namespace Grpc.IntegrationTesting
                 case "status_code_and_message":
                     await RunStatusCodeAndMessageAsync(client);
                     break;
+                case "unimplemented_method":
+                    RunUnimplementedMethod(new UnimplementedService.UnimplementedServiceClient(channel));
+                    break;
                 default:
                     throw new ArgumentException("Unknown test case " + options.TestCase);
             }
@@ -577,6 +580,16 @@ namespace Grpc.IntegrationTesting
             Console.WriteLine("Passed!");
         }
 
+        public static void RunUnimplementedMethod(UnimplementedService.IUnimplementedServiceClient client)
+        {
+            Console.WriteLine("running unimplemented_method");
+            var e = Assert.Throws<RpcException>(() => client.UnimplementedCall(new Empty()));
+
+            Assert.AreEqual(StatusCode.Unimplemented, e.Status.StatusCode);
+            Assert.AreEqual("", e.Status.Detail);
+            Console.WriteLine("Passed!");
+        }
+
         private static Payload CreateZerosPayload(int size)
         {
             return new Payload { Body = ByteString.CopyFrom(new byte[size]) };

src/csharp/Grpc.IntegrationTesting/InteropClientServerTest.cs

@@ -144,5 +144,11 @@ namespace Grpc.IntegrationTesting
         {
             await InteropClient.RunStatusCodeAndMessageAsync(client);
         }
+
+        [Test]
+        public void UnimplementedMethod()
+        {
+            InteropClient.RunUnimplementedMethod(UnimplementedService.NewClient(channel));
+        }
     }
 }