Example for the CQRS CodelyTV Pro course. Full repo: https://github.com/CodelyTV/cqrs-ddd-scala-example/blob/master/src/test/scala/tv/codely/cqrs_ddd_scala_example/acceptance/AsyncUserGreetFinderTest.scala

AsyncUserGreetFinderTest.scala

package tv.codely.cqrs_ddd_scala_example.acceptance

import java.util.UUID

import scala.reflect.classTag
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext.Implicits.global

import cats.implicits._
import org.joda.time.DateTime
import org.scalatest.concurrent.ScalaFutures
import org.scalatest.Matchers._
import org.scalatest._
import org.scalatest.concurrent.PatienceConfiguration.Timeout
import org.scalatest.time.{Seconds, Span}
import tv.codely.cqrs_ddd_scala_example.bus.domain.QueryBus
import tv.codely.cqrs_ddd_scala_example.user_greet.application.generate.{
  FindUserGreetQuery,
  FindUserGreetQueryHandler,
  UserGreetFinder
}
import tv.codely.cqrs_ddd_scala_example.user_greet.infrastructure.InAsyncDelayedMemoryUserRepository

final class AsyncUserGreetFinderTest extends WordSpec with ScalaFutures with GivenWhenThen {

  "UserGreetGenerator with an AsyncQueryBus" should {
    "not block the execution flow until getting a response from a slow repository" in {

      Given("a UserGreetGenerator with a user repository with a notable delay")

      val notableDelay                  = 10.seconds
      val userRepository                = new InAsyncDelayedMemoryUserRepository(notableDelay)
      val userGreetGeneratorWithDelay   = new UserGreetFinder(userRepository)
      val generateUserGreetQueryHandler = new FindUserGreetQueryHandler(userGreetGeneratorWithDelay)

      And("an AsyncQueryBus which doesn't block the execution flow until getting a response")

      val queryBus = new QueryBus(
        Map(
          classTag[FindUserGreetQuery] -> generateUserGreetQueryHandler
        ))

      When("we ask the GenerateUserGreetQuery to the AsyncQueryBus")

      val query = FindUserGreetQuery(
        UUID.randomUUID(),
        DateTime.now(),
        UUID.fromString("1646fd5c-de2b-435f-b20f-ad1f50924dfe"))

      val futureGreeting = queryBus.ask(query)

      println("Query asked to the async query bus")

      Then("it should say hello to someone")

      futureGreeting.futureValue(Timeout(Span(15, Seconds))).greet
    }
  }
}