add tests demonstrating how to mock client stubs
diff --git a/src/csharp/tests.json b/src/csharp/tests.json
index 60f67ff..dc1f085 100644
--- a/src/csharp/tests.json
+++ b/src/csharp/tests.json
@@ -41,6 +41,7 @@
     "Grpc.Core.Tests.UserAgentStringTest"
   ],
   "Grpc.Examples.Tests": [
+    "Math.Tests.MathClientMockableTest",
     "Math.Tests.MathClientServerTest"
   ],
   "Grpc.HealthCheck.Tests": [