add C# test demoing custom error details
diff --git a/src/csharp/tests.json b/src/csharp/tests.json
index 707d140..bc6adbb 100644
--- a/src/csharp/tests.json
+++ b/src/csharp/tests.json
@@ -42,6 +42,7 @@
     "Grpc.HealthCheck.Tests.HealthServiceImplTest"
   ],
   "Grpc.IntegrationTesting": [
+    "Grpc.IntegrationTesting.CustomErrorDetailsTest",
     "Grpc.IntegrationTesting.GeneratedClientTest",
     "Grpc.IntegrationTesting.GeneratedServiceBaseTest",
     "Grpc.IntegrationTesting.HistogramTest",