How to unit test streaming RPCs

[jonnylangefeld]

I have a unit test file for every service. In the unit test I instantiate the server like

server = NewHello()

And then just call the functions directly. Check below for a working example

unfold for working unit test

var _ = Describe("Hello", func() {
	var server *Hello

	BeforeEach(func() {
		server = NewHello()
	})

	Context("SayHello", func() {
		It("returns a response", func() {
			resp, err := server.SayHello(nil, &connect.Request[lifev1.SayHelloRequest]{
				Msg: &lifev1.SayHelloRequest{
					Name: "Test Name",
				},
			})
			Expect(err).NotTo(HaveOccurred())
			Expect(resp.Msg.Message).To(Equal("Hello Test Name"))
		})

		It("returns an error if the name is missing", func() {
			_, err := server.SayHello(nil, &connect.Request[lifev1.SayHelloRequest]{
				Msg: &lifev1.SayHelloRequest{
					Name: "",
				},
			})
			Expect(err).To(HaveOccurred())
			Expect(err.Error()).To(ContainSubstring("missing name"))
		})
	})

})

But now for a different service I have an rpc with a stream:

func (s *MyService) WatchUnits(_ context.Context, in *connect.Request[lifev1.WatchUnitsRequest], stream *connect.ServerStream[lifev1.WatchUnitsResponse]) error {
	for update := range s.updates {
		if err := stream.Send(update); err != nil {
			return err
		}
	}
	return nil
}

(s.updates is a channel)

How can I test this?

This is my attempt, but it's not quite right yet:

	Describe("WatchUnits", func() {
		It("receives messages on the stream", func() {
			stream := &connect.ServerStream[lifev1.WatchUnitsResponse]{}
			go func() {
				Expect(server.WatchUnits(nil, nil, stream)).NotTo(HaveOccurred())
			}()
			v := &lifev1.WatchUnitsResponse{}
			go func() {
				server.updates <- v
			}()
			Expect(stream).Should(Receive(v))
		})
	})

[emcfarlane]

Hey @jonnylangefeld , currently these constructors for the Stream types aren't exported. See the docs for the stream types: e.g. https://pkg.go.dev/connectrpc.com/connect#BidiStream

doesn't currently have an exported constructor.

To test handlers the current recommended way is to use the net/http/httptest package and create a server with a corresponding client to invoke the server. See the tests in the connect package as examples:

connect-go/client_ext_test.go

Line 446 in 297532d

svr := httptest.NewUnstartedServer(http.HandlerFunc(func(respWriter http.ResponseWriter, req *http.Request) {