pekko/akka-stream-testkit/src/test/scala/akka/stream/testkit2/TwoStreamsSetup.scala

package akka.stream.testkit2

import akka.stream.MaterializerSettings
import akka.stream.scaladsl2._
import akka.stream.testkit.{ StreamTestKit, AkkaSpec }
import org.reactivestreams.Publisher

import scala.util.control.NoStackTrace

abstract class TwoStreamsSetup extends AkkaSpec {

  val settings = MaterializerSettings(system)
    .withInputBuffer(initialSize = 2, maxSize = 2)
    .withFanOutBuffer(initialSize = 2, maxSize = 2)

  implicit val materializer = FlowMaterializer(settings)

  case class TE(message: String) extends RuntimeException(message) with NoStackTrace

  val TestException = TE("test")

  type Outputs

  def operationUnderTestLeft(): JunctionInPort[Int] { type NextT = Outputs }
  def operationUnderTestRight(): JunctionInPort[Int] { type NextT = Outputs }

  def setup(p1: Publisher[Int], p2: Publisher[Int]) = {
    val subscriber = StreamTestKit.SubscriberProbe[Outputs]()
    FlowGraph { implicit b ⇒
      import FlowGraphImplicits._
      val left = operationUnderTestLeft()
      val right = operationUnderTestRight()
      val x = Source(p1) ~> left ~> Flow[Outputs] ~> Sink(subscriber)
      Source(p2) ~> right
    }.run()

    subscriber
  }

  def failedPublisher[T]: Publisher[T] = StreamTestKit.errorPublisher[T](TestException)

  def completedPublisher[T]: Publisher[T] = StreamTestKit.emptyPublisher[T]

  def nonemptyPublisher[T](elems: Iterator[T]): Publisher[T] = Source(elems).runWith(Sink.publisher)

  def soonToFailPublisher[T]: Publisher[T] = StreamTestKit.lazyErrorPublisher[T](TestException)

  def soonToCompletePublisher[T]: Publisher[T] = StreamTestKit.lazyEmptyPublisher[T]

  def commonTests() = {
    "work with two immediately completed publishers" in {
      val subscriber = setup(completedPublisher, completedPublisher)
      subscriber.expectCompletedOrSubscriptionFollowedByComplete()
    }

    "work with two delayed completed publishers" in {
      val subscriber = setup(soonToCompletePublisher, soonToCompletePublisher)
      subscriber.expectCompletedOrSubscriptionFollowedByComplete()
    }

    "work with one immediately completed and one delayed completed publisher" in {
      val subscriber = setup(completedPublisher, soonToCompletePublisher)
      subscriber.expectCompletedOrSubscriptionFollowedByComplete()
    }

    "work with two immediately failed publishers" in {
      val subscriber = setup(failedPublisher, failedPublisher)
      subscriber.expectErrorOrSubscriptionFollowedByError(TestException)
    }

    "work with two delayed failed publishers" in {
      val subscriber = setup(soonToFailPublisher, soonToFailPublisher)
      subscriber.expectErrorOrSubscriptionFollowedByError(TestException)
    }

    // Warning: The two test cases below are somewhat implementation specific and might fail if the implementation
    // is changed. They are here to be an early warning though.
    "work with one immediately failed and one delayed failed publisher (case 1)" in {
      val subscriber = setup(soonToFailPublisher, failedPublisher)
      subscriber.expectErrorOrSubscriptionFollowedByError(TestException)
    }

    "work with one immediately failed and one delayed failed publisher (case 2)" in {
      val subscriber = setup(failedPublisher, soonToFailPublisher)
      subscriber.expectErrorOrSubscriptionFollowedByError(TestException)
    }
  }

}