Akka Streams, StreamConverters and System.in

Question

I'm using Scala 2.13.7 with Akka Streams 2.6.17.

I have this very basic Akka Stream. It takes what the user types (System.in), applies toUpperCase function and finally the string is printed using System.out:

    val stdInSource: Source[ByteString, Future[IOResult]] = StreamConverters.fromInputStream(() => System.in)
    val stdOutSink: Sink[ByteString, Future[IOResult]]    = StreamConverters.fromOutputStream(() => System.out)
    val dummyFlow: Flow[ByteString, ByteString, NotUsed] = {
      Flow[ByteString].map(x => ByteString(x.utf8String.toUpperCase))
    }

    stdInSource
      .via(dummyFlow)
      .runWith(stdOutSink)

Let's say I want to wrap this code in a function something like this:

  def myStream(input: () => InputStream)(implicit system: ActorSystem): Future[IOResult] = {
    
    val stdOutSink: Sink[ByteString, Future[IOResult]]   = StreamConverters.fromOutputStream(() => System.out)
    val dummyFlow: Flow[ByteString, ByteString, NotUsed] = {
      Flow[ByteString].map(x => ByteString(x.utf8String.toUpperCase))
    }

    StreamConverters
      .fromInputStream(input)
      .via(dummyFlow)
      .runWith(stdOutSink)
  }

Then I can invoke it like this:

myStream(() => System.in)

My question is: if I want to create unit tests, how can I pass a List[String] to myStream? I mean how can I convert the List[String] into the same type as myStream parameter? (() => InputStream)

Akka Streams, StreamConverters and System.in

0 Answers0