abstract the notion of sycn/async result : solution

Repository.scala

import scala.concurrent.Future

trait Repository[ResultWrapper[_], AggregateRoot] {
	def create(root: AggregateRoot): ResultWrapper[String]
	def retrieve(id: String): ResultWrapper[Option[AggregateRoot]]
	def retrieveAll(): ResultWrapper[Set[AggregateRoot]]
	def update(root: AggregateRoot): ResultWrapper[ServerResponse]
	def delete(root: AggregateRoot): ResultWrapper[ServerResponse]
}

trait ServerResponse

object SyncResultWrapperModule {
	type SyncResult[X] = X
}

object AsyncResultWrapperModule {   // just a syntaxic sugar to be symetric with type SyncResult
	type AsyncResult[X] = Future[X]
}

/**
 * https://groups.google.com/forum/#!topic/paris-scala-user-group/VxhUOheC0vQ
 * http://www.chuusai.com/2011/06/09/scala-union-types-curry-howard/
 * http://rapture.io/exceptions
 */

RepositoryTest.scala

import org.scalatest.{Matchers, FunSuite}
import usetypes.AsyncResultWrapperModule.AsyncResult
import usetypes.SyncResultWrapperModule.SyncResult

import scala.concurrent.Future

class RepositoryTest extends FunSuite with Matchers {
	trait User // a stub aggregate root to simulate repository

	test("a sync repository") {
		object UserSyncRepository extends Repository[SyncResult, User] {
			override def create(root: User): String = "ok"
			override def update(root: User): ServerResponse = ???
			override def retrieveAll(): Set[User] = ???
			override def delete(root: User): ServerResponse = ???
			override def retrieve(id: String): Option[User] = ???
		}

		UserSyncRepository.create(null) shouldBe "ok"
	}

	test("an async repository") {
		import concurrent.ExecutionContext.Implicits.global
		import concurrent.Await.result
		import concurrent.duration._

		object UserAsyncRepository extends Repository[AsyncResult, User] {
			override def create(root: User): Future[String] = Future("ok")
			override def update(root: User): Future[ServerResponse] = ???
			override def retrieveAll(): Future[Set[User]] = ???
			override def delete(root: User): Future[ServerResponse] = ???
			override def retrieve(id: String): Future[Option[User]] = ???
		}

		result(UserAsyncRepository.create(null), 1 second) shouldBe "ok"
	}
}