How to unit test grpc-java server implementation functions?

Question

I have an implementation of GRPC-java server code, but I didn't find the example code to unit test the StreamObserver. Does anyone know the right way to unit test the function?

public class RpcTrackDataServiceImpl implements TrackDataServiceGrpc.TrackDataService {
    @Override
    public void getTracks(GetTracksRequest request, StreamObserver < GetTracksResponse > responseObserver) {
        GetTracksResponse reply = GetTracksResponse
            .newBuilder()
            .addTracks(TrackInfo.newBuilder()
                .setOwner("test")
                .setTrackName("test")
                .build())
            .build();
        responseObserver.onNext(reply);
        responseObserver.onCompleted();
    }
}

Answer 1

@RunWith(JUnit4.class)
public class HelloWorldServerTest {
  /**
   * This rule manages automatic graceful shutdown for the registered servers and channels at the
   * end of test.
   */
  @Rule
  public final GrpcCleanupRule grpcCleanup = new GrpcCleanupRule();

  /**
   * To test the server, make calls with a real stub using the in-process channel, and verify
   * behaviors or state changes from the client side.
   */
  @Test
  public void greeterImpl_replyMessage() throws Exception {
    // Generate a unique in-process server name.
    String serverName = InProcessServerBuilder.generateName();

    // Create a server, add service, start, and register for automatic graceful shutdown.
    grpcCleanup.register(InProcessServerBuilder
        .forName(serverName).directExecutor().addService(new GreeterImpl()).build().start());

    GreeterGrpc.GreeterBlockingStub blockingStub = GreeterGrpc.newBlockingStub(
        // Create a client channel and register for automatic graceful shutdown.
        grpcCleanup.register(InProcessChannelBuilder.forName(serverName).directExecutor().build()));


    HelloReply reply =
        blockingStub.sayHello(HelloRequest.newBuilder().setName( "test name").build());

    assertEquals("Hello test name", reply.getMessage());
  }
}

https://github.com/grpc/grpc-java/blob/master/examples/src/test/java/io/grpc/examples/helloworld/HelloWorldServerTest.java

Answer 2

I ended up with a solution to create a FakeStreamObserver that implements the StreamObserver interface.
The FakeStreamObserver is passed in to execute onNext, onCompleted etc.
I'm not sure if this is the best way or not.