Stream Testkit expectNextType ?

[Derek Wyatt]

Hi guys,

I've been writing some tests for my stream code and have run up against a situation where I would like to have expectNextType.  I've implemented this myself with a pimp, but I'm wondering if there's a better way?

  implicit class ProbeExtension[T](val p: Probe[T]) {
    def expectNextType[A](implicit t: ClassTag[A]): p.Self = {
      p.expectNextPF {
        case a: A =>
        case x => fail(s"Expected a $t type but got a ${x.getClass.getName}")
      }
      p
    }
  }

This is mostly useful when the 'A' in question is a derivation of Try[_].  I tend to write expectNextType[Failure[_]] in these cases.  And, just to give some context as to why I would want to do that: My flow components might return a Try, which I then pass through a special handling / logging flow, which transforms them to a List that is composed with a mapConcat. So...

val flowReturningTry: Flow[T, Try[U], NotUsed] = ...
val handlingAndLogging: Flow[Try[U], U, NotUsed] = Flow[Try[U]].mapConcat { /* List(u) or List(), depending on the Try */ }
val composed: Flow[T, U, NotUsed] = flowReturningTry.mapConcat(handlingAndLogging)

Now, when testing flowReturningTry in isolation, the expectNextType is useful.

Cheers and thanks,
Derek

[Patrik Nordwall]

Hi Derek,

Sounds like a great addition. Will you take a stab at it?

/Patrik

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Patrik Nordwall
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Lightbend -  Reactive apps on the JVM
Twitter: @patriknw

[Derek Wyatt]

Alright. I'll play around with these over the next few days and send you a PR.

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[Patrik Nordwall]

Thanks, Derek