testserver program is a simple server that can be used for testing RPC clients such
grpcurl. It implements an RPC interface that is defined in
grpcurl's testing package and also exposes the implementation that is defined in that same package. This is the same test interface and implementation that is used in unit tests for
For a possibly more interesting test server, take a look at
bankdemo, which is a demo gRPC app that provides a more concrete RPC interface, including full-duplex bidirectional streaming methods, plus an example implementation.