add Grpc.Tools test for generating for .proto with the same name
diff --git a/test/distrib/csharp/DistribTest/Program.cs b/test/distrib/csharp/DistribTest/Program.cs
index bda7b21..79c10ac 100644
--- a/test/distrib/csharp/DistribTest/Program.cs
+++ b/test/distrib/csharp/DistribTest/Program.cs
@@ -53,6 +53,14 @@
                 server.ShutdownAsync().Wait();
             }
         }
+
+        // Test that codegen works well in case the .csproj has .proto files
+        // of the same name, but under different directories (see #17672).
+        // This method doesn't need to be used, it is enough to check that it builds.
+        private static object CheckDuplicateProtoFilesAreOk()
+        {
+            return new DuplicateProto.MessageFromDuplicateProto();
+        }
     }
 
     class GreeterImpl : Greeter.GreeterBase
diff --git a/test/distrib/csharp/DistribTest/duplicate_proto/testcodegen.proto b/test/distrib/csharp/DistribTest/duplicate_proto/testcodegen.proto
new file mode 100644
index 0000000..cb767cb
--- /dev/null
+++ b/test/distrib/csharp/DistribTest/duplicate_proto/testcodegen.proto
@@ -0,0 +1,23 @@
+// Copyright 2019 The gRPC Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Test that codegen works well in case the .csproj has .proto files
+// of the same name, but under different directories (see #17672).
+syntax = "proto3";
+
+package duplicate_proto;
+
+message MessageFromDuplicateProto {
+  string name = 1;
+}