Inputs

FauxRPC offers versatile ways to define the services it emulates. Whether you have Protobuf files, descriptor sets, a live gRPC server, or even Buf Schema Registry images, you can seamlessly provide the necessary input for FauxRPC to generate mock responses. This flexibility empowers you to test and develop against various scenarios without relying on actual backend implementations.

From Protobuf files

If you have .proto source files, you can use buf to build a descriptor set and then use it with FauxRPC.

Make an example.proto file (or use a file that already exists):

syntax = "proto3";

package greet.v1;

message GreetRequest {
  string name = 1;
}

message GreetResponse {
  string greeting = 1;
}

service GreetService {
  rpc Greet(GreetRequest) returns (GreetResponse) {}
}

Create a descriptors file and use it to start the FauxRPC server:

$ buf build ./example.proto -o ./example.binpb
$ fauxrpc run --schema=./example.binpb
2024/08/17 08:01:19 INFO Listening on http://127.0.0.1:6660
2024/08/17 08:01:19 INFO See available methods: buf curl --http2-prior-knowledge http://127.0.0.1:6660 --list-methods

Done! It’s that easy. Now you can call the service with any tooling that supports gRPC, gRPC-Web, or connect. So buf curl, grpcurl, Postman, Insomnia all work fine!

$ buf curl --http2-prior-knowledge http://127.0.0.1:6660/greet.v1.GreetService/Greet
{
  "greeting":  "3 wolf moon fashion axe."
}

Using Descriptor Sets

If you already have a Protobuf descriptor set file (commonly with a .binpb or .json extension), you can provide it directly to FauxRPC. For more about descriptor sets, see the Buf documentation.

$ fauxrpc run --schema=./example.binpb

Using Server Reflection

If there’s an existing gRPC service running that you want to emulate, you can use server reflection to start the FauxRPC service:

$ fauxrpc run --schema=https://demo.connectrpc.com

From BSR (Buf Schema Registry)

Buf has a schema registry where many schemas are hosted. You can use images from the registry directly with FauxRPC.

$ fauxrpc run --schema=buf.build/bufbuild/registry

This will start a fake version of the BSR API by downloading descriptors for bufbuild/registry from the BSR and using them with FauxRPC. Very meta.

Multiple Sources

You can define this --schema option as many times as you want. That means you can add services from multiple descriptors and even mix and match from descriptors and from server reflection:

$ fauxrpc run --schema=https://demo.connectrpc.com --schema=./example.binpb

All the same inputs described above also work for fauxrpc curl.