stream-test

Chapter 7: Working with Akka Streams

Testing Streams

Here's examples on how to test streams with different techniques.

Dependencies

Akka Streams have TestKit test framework for testing it. Here's list of dependencies you will need for testing Akka Streams:

libraryDependencies ++= Seq(
  "com.typesafe.akka" %% "akka-actor" % "2.4.4",
  "com.typesafe.akka" %% "akka-stream" % "2.4.4",
  "com.typesafe.akka" %% "akka-stream-testkit" % "2.4.4",
  "org.scalatest" %% "scalatest" % "2.2.6" % "test",
  "com.typesafe.akka" %% "akka-testkit" % "2.4.4" % "test"
)

Migration from experimental version 1.x to 2.4.x

In class StreamActorSpec have to change old code. Following apply() function was removed from Source object of Akka Stream:

val source = Source(0.millis, 200.millis, Tick)

It was replaced by tick() function:

val source = Source.tick(0.millis, 200.millis, Tick)

In class StreamKitSpec following call with empty parameter list was not working:

sourceUnderTest.runWith(TestSink.probe[Int]())

ActorSystem argument should be passed explicitly:

sourceUnderTest.runWith(TestSink.probe[Int](system))

In same class following code is causing test failure:

sourceUnderTest.runWith(TestSink.probe[Int]())
.request(2)
.expectNext(2, 4)
.expectComplete()

Test fails with the following failure message:

java.lang.AssertionError: assertion failed: timeout (3 seconds) during expectMsg while waiting for OnComplete

It looks like stream testkit have a bug which causes expectComplete() to fail after extectNext() call. Here's the link to reported issue.