How do you test gRPC services?

Testing gRPC services involves multiple levels: (1) Unit testing — test service handler functions directly without a gRPC server: call the handler function with a mock context and request, assert on the response; (2) Integration testing — start an in-process gRPC server on a buffer (bufconn in Go), create a real client, and call methods. No network involved, but tests actual gRPC lifecycle; (3) Contract testing — verify that client and server agree on the Protobuf schema using the Buf registry or Protolock; (4) Manual testing tools — grpcurl (cURL for gRPC), Postman, BloomRPC, Evans; (5) Mocking — generate mock implementations of service interfaces for dependency injection in tests; (6) Load testing — ghz (gRPC load testing tool) generates concurrent RPC calls and measures throughput and latency percentiles. Always test streaming methods with multiple messages and cancellation scenarios.