CODEWITHSUNDEEP
scalascalatestakka-stream
gyoho
gyoho

Reputation: 899

Akka Stream Graphs - How to test PartitionWith from akka.stream.contrib

I wrote a simple test to explore the PartitionWith graph functionality from akka.stream.contrib. Here is the code snippet:

class Scratch
    extends TestKit(ActorSystem("PartitionWith"))
    with WordSpecLike
    with ScalaFutures
    with Eventually
    with Matchers {

  "PartitionWith" should {
    "split source" in {
      val source: Source[Either[Int, String], NotUsed] = Source(List(Left(1), Right("one")))
      val leftHeadSink = Sink.head[Int]
      val rightHeadSink = Sink.head[String]

      val flow = RunnableGraph.fromGraph(GraphDSL.create(source, leftHeadSink, rightHeadSink)((_, _, _)) {
        implicit builder: GraphDSL.Builder[(NotUsed, Future[Int], Future[String])] => (s, l, r) =>
          import GraphDSL.Implicits._

          val pw = builder.add(PartitionWith.apply[Either[Int, String], Int, String](identity))

          s ~> pw.in
          pw.out0 ~> l.in
          pw.out1 ~> r.in

          ClosedShape
      })

      val event = flow.run()
      event._2.futureValue shouldBe 1     // first check
      event._3.futureValue shouldBe "one" // second check
    }

When I run the above test, it throws me this error:

The future returned an exception of type: java.util.NoSuchElementException, with message: head of empty stream.
org.scalatest.exceptions.TestFailedException: The future returned an exception of type: java.util.NoSuchElementException, with message: head of empty stream.

It seems like it fails in the second check because the rightHeadSink is empty. I'm wondering if the Right("one") in Source(List(Left(1), Right("one"))) is never processed??

How do I fix this?

Upvotes: 0

Views: 380

Answers (1)

Stefano Bonetti
Stefano Bonetti

Reputation: 9023

As the first Sink.head completes, it seems like the whole stream is completed, so the second sink fails to retrieve its element.

Try to test with 2 Sink.seqs instead of 2 Sink.heads to avoid a precocious termination of your stream.

Upvotes: 0

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