How to test client-side Akka HTTP

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挽巷
挽巷 2021-02-07 09:55

I\'ve just started testing out the Akka HTTP Request-Level Client-Side API (Future-Based). One thing I\'ve been struggling to figure out is how to write a unit test for this. Is

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  •  囚心锁ツ
    2021-02-07 10:45

    I think in general terms you've already hit on the fact that the best approach is to mock the response. In Scala, this can be done using Scala Mock http://scalamock.org/

    If you arrange your code so that your instance of akka.http.scaladsl.HttpExt is dependency injected into the code which uses it (e.g. as a constructor parameter), then during testing you can inject an instance of mock[HttpExt] rather than one built using the Http apply method.

    EDIT: I guess this was voted down for not being specific enough. Here is how I would structure the mocking of your scenario. It is made a little more complicated by all the implicitis.

    Code in main:

    import akka.actor.ActorSystem
    import akka.http.scaladsl.Http
    import akka.http.scaladsl.model.{Uri, HttpResponse, HttpRequest}
    import akka.http.scaladsl.unmarshalling.Unmarshal
    import akka.stream.ActorMaterializer
    
    import scala.concurrent.{ExecutionContext, Future}
    
    trait S3BucketTrait {
    
      type HttpResponder = HttpRequest => Future[HttpResponse]
    
      def responder: HttpResponder
    
      implicit def actorSystem: ActorSystem
    
      implicit def actorMaterializer: ActorMaterializer
    
      implicit def ec: ExecutionContext
    
      def sampleTextFile(uri: Uri): Future[String] = {
    
        val responseF = responder(HttpRequest(uri = uri))
        responseF.flatMap { response => Unmarshal(response.entity).to[String] }
      }
    }
    
    class S3Bucket(implicit val actorSystem: ActorSystem, val actorMaterializer: ActorMaterializer) extends S3BucketTrait {
    
      override val ec: ExecutionContext = actorSystem.dispatcher
    
      override def responder = Http().singleRequest(_)
    }
    

    Code in test:

    import akka.actor.ActorSystem
    import akka.http.scaladsl.model._
    import akka.stream.ActorMaterializer
    import akka.testkit.TestKit
    import org.scalatest.{BeforeAndAfterAll, WordSpecLike, Matchers}
    import org.scalamock.scalatest.MockFactory
    import scala.concurrent._
    import scala.concurrent.duration._
    import scala.concurrent.Future
    
    class S3BucketSpec extends TestKit(ActorSystem("S3BucketSpec"))
    with WordSpecLike with Matchers with MockFactory with BeforeAndAfterAll  {
    
    
      class MockS3Bucket(reqRespPairs: Seq[(Uri, String)]) extends S3BucketTrait{
    
        override implicit val actorSystem = system
    
        override implicit val ec = actorSystem.dispatcher
    
        override implicit val actorMaterializer = ActorMaterializer()(system)
    
        val mock = mockFunction[HttpRequest, Future[HttpResponse]]
    
        override val responder: HttpResponder = mock
    
        reqRespPairs.foreach{
          case (uri, respString) =>
            val req = HttpRequest(HttpMethods.GET, uri)
            val resp = HttpResponse(status = StatusCodes.OK, entity = respString)
            mock.expects(req).returning(Future.successful(resp))
        }
      }
    
      "S3Bucket" should {
    
        "Marshall responses to Strings" in {
          val mock = new MockS3Bucket(Seq((Uri("http://example.com/1"), "Response 1"), (Uri("http://example.com/2"), "Response 2")))
          Await.result(mock.sampleTextFile("http://example.com/1"), 1 second) should be ("Response 1")
          Await.result(mock.sampleTextFile("http://example.com/2"), 1 second) should be ("Response 2")
        }
      }
    
      override def afterAll(): Unit = {
        val termination = system.terminate()
        Await.ready(termination, Duration.Inf)
      }
    }
    

    build.sbt dependencies:

    libraryDependencies += "com.typesafe.akka" % "akka-http-experimental_2.11" % "2.0.1"
    
    libraryDependencies += "org.scalamock" %% "scalamock-scalatest-support" % "3.2" % "test"
    
    libraryDependencies += "org.scalatest" % "scalatest_2.11" % "2.2.6"
    
    libraryDependencies += "com.typesafe.akka" % "akka-testkit_2.11" % "2.4.1"
    

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