Add test target for codegen.

Make all test messages empty since we are not testing protobuf
generator.
diff --git a/compiler/test/test.proto b/compiler/test/test.proto
new file mode 100644
index 0000000..1df34a5
--- /dev/null
+++ b/compiler/test/test.proto
@@ -0,0 +1,53 @@
+// A simple service definition for testing the protoc plugin.
+syntax = "proto2";
+
+package grpc.testing;
+
+option java_package = "com.google.net.stubby.testing.integration";
+
+message SimpleRequest {
+}
+
+message SimpleResponse {
+}
+
+message StreamingInputCallRequest {
+}
+
+message StreamingInputCallResponse {
+}
+
+message StreamingOutputCallRequest {
+}
+
+message StreamingOutputCallResponse {
+}
+
+service TestService {
+  // One request followed by one response.
+  // The server returns the client payload as-is.
+  rpc UnaryCall(SimpleRequest) returns (SimpleResponse);
+
+  // One request followed by a sequence of responses (streamed download).
+  // The server returns the payload with client desired type and sizes.
+  rpc StreamingOutputCall(StreamingOutputCallRequest)
+      returns (stream StreamingOutputCallResponse);
+
+  // A sequence of requests followed by one response (streamed upload).
+  // The server returns the aggregated size of client payload as the result.
+  rpc StreamingInputCall(stream StreamingInputCallRequest)
+      returns (StreamingInputCallResponse);
+
+  // A sequence of requests with each request served by the server immediately.
+  // As one request could lead to multiple responses, this interface
+  // demonstrates the idea of full duplexing.
+  rpc FullDuplexCall(stream StreamingOutputCallRequest)
+      returns (stream StreamingOutputCallResponse);
+
+  // A sequence of requests followed by a sequence of responses.
+  // The server buffers all the client requests and then serves them in order. A
+  // stream of responses are returned to the client when the server starts with
+  // first request.
+  rpc HalfDuplexCall(stream StreamingOutputCallRequest)
+      returns (stream StreamingOutputCallResponse);
+}