How to test methods that return Future?

Question

I\'d like to test a method that returns a Future. My attempts were as follows:

import  org.specs2.mutable.Specification
import scala.concurrent.Exec         


        

Answer 1

There is a nice thing for that in specs2 - implicit await method for Future[Result]. If you take advantage of future transformations you can write like this:

"save notification" in {
  notificationDao.saveNotification(notification) map { writeResult =>
    writeResult.ok must be equalTo (true)
  } await
}

Future composition comes to the rescue when some data arrangement with async functions is needed:

"get user notifications" in {
  {
    for {
      _ <- notificationDao.saveNotifications(user1Notifications)
      _ <- notificationDao.saveNotifications(user2Notifications)
      foundUser1Notifications <- notificationDao.getNotifications(user1)
    } yield {
      foundUser1Notifications must be equalTo (user1Notifications)
    }
  } await
}

Note how we have to use an additional block around for-comprehension to convince compiler. I think it's noisy, so if we turn await method in a function we come up with a nicer syntax:

def awaiting[T]: Future[MatchResult[T]] => Result = { _.await }

"get user notifications" in awaiting {
  for {
    _ <- notificationDao.saveNotifications(user1Notifications)
    _ <- notificationDao.saveNotifications(user2Notifications)
    foundUser1Notifications <- notificationDao.getNotifications(user1)
  } yield {
    foundUser1Notifications must be equalTo (user1Notifications)
  }
}