How to create "fake" client stub?

[lhluo]

Hi team, new to grpc-kotlin so would appreciate any help!

I'm going through the gRPC kotlin tutorial here. It seems easy to create a client stub and call it like follows:

val channel = ManagedChannelBuilder.forAddress("localhost", 8980).usePlaintext().build()
val stub = RouteGuideCoroutineStub(channel)

However, I can't figure out how to create a "fake" stub for testing / running locally. Is there a way to create a fake RouteGuideCoroutineStub object? Or a way of binding this stub to call a fake in-process server?

I see in the non-kt offering of grpc that there exists a function RouteGuideCoroutine.newFutureStub that would let us instantiate a new stub. Does something like this exist for grpc Kt?

fyi (also posted this question to stack overflow)

[lowasser]

Hi! In future, please only post your question to one place.

The recommended practice for testing is to use a fake in-process server, for which you can use the same API as Java.

To instantiate a new stub, use the constructor; you can see an example here.

[lhluo]

@lowasser thanks, can you provide an example of how to use the java api to create an instance of RouteGuideCoroutineStub? Like I mentioned, I'd like to use this outside of tests in a local instance. My code depends on the type RouteGuideCoroutineStub, but it's not an interface I can override to provide fake data.

[lowasser]

You don't use the Java API to create an instance of RouteGuideCoroutineStub, you create a custom instance of the server (possibly with fake data), and then use the Java API to install it. Something like

val uniqueName = InProcessServerBuilder.generateName()
val server = InProcessServerBuilder.forName(uniqueName)
       .directExecutor() // directExecutor is fine for unit tests
       .addService(/** some custom instance of RouteGuideCoroutineImpl */)
       .build().start()
val channel = InProcessChannelBuilder.forName(uniqueName)
       .directExecutor()
       .build()
val stub = RouteGuideCoroutineStub(channel)

[jamesward]

The example test might also be helpful: https://github.com/grpc/grpc-kotlin/blob/master/examples/server/src/test/kotlin/io/grpc/examples/routeguide/RouteGuideServerTest.kt