如何测试return Future 的方法？

Question

我想测试一个 returns 和 Future 的方法。我的尝试如下：

import  org.specs2.mutable.Specification
import scala.concurrent.ExecutionContext.Implicits.global
import scala.util.{Failure, Success}

class AsyncWebClientSpec extends Specification{

  "WebClient when downloading images" should {
    "for a valid link return non-zero content " in {
      val testImage = AsyncWebClient.get("https://www.google.cz/images/srpr/logo11ww.png")
      testImage.onComplete { res => 
        res match {
          case Success(image) => image must not have length(0)
          case _ =>
        }
        AsyncWebClient.shutDown
      }
    }
  }
}

除了我无法使这段代码工作之外，我想可能有更好的方法来使用面向 Future 的匹配器来测试期货。

如何在specs2中正确地做到这一点？

Answer 1

onComplete returns Unit，所以代码块 returns 立即结束，测试在能够做任何事情之前结束。为了正确测试 Future 的结果，您需要阻塞直到它完成。您可以使用 Await 并设置最大等待时间 Duration。

import scala.concurrent._
import scala.concurrent.duration._

Await.result(testImage, Duration("10 seconds")) must not have length(0)

Answer 2

您可以使用 Matcher.await 方法将 Matcher[T] 转换为 Matcher[Future[T]]:

val testImage: Future[String] =
   AsyncWebClient.get("https://www.google.cz/images/srpr/logo11ww.png")  

// you must specify size[String] here to help type inference
testImage must not have size[String](0).await

// you can also specify a number of retries and duration between retries
testImage must not have size[String](0).await(retries = 2, timeout = 2.seconds)

// you might also want to check exceptions in case of a failure
testImage must throwAn[Exception].await

Answer 3

在 specs2 中有一件好事 - Future[Result] 的隐式 await 方法。如果你利用未来的转换，你可以这样写：

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

当需要使用异步函数进行一些数据排列时，未来的组合会派上用场：

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

请注意，我们必须如何使用额外的块来理解 for-comprehension 来说服编译器。我认为它很吵，所以如果我们在函数中使用 await 方法，我们会想出一个更好的语法：

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)
  }
}

Answer 4

想知道为什么@etorreborre 没有提到 "eventually"

见https://github.com/etorreborre/specs2/blob/master/tests/src/test/scala/org/specs2/matcher/EventuallyMatchersSpec.scala#L10-L43

class EventuallyMatchersSpec extends Specification with FutureMatchers with ExpectationsDescription { section("travis")
addParagraph { """
`eventually` can be used to retry any matcher until a maximum number of times is reached
or until it succeeds.
""" }

  "A matcher can match right away with eventually" in {
    1 must eventually(be_==(1))
  }
  "A matcher can match right away with eventually, even if negated" in {
    "1" must not (beNull.eventually)
  }
  "A matcher will be retried automatically until it matches" in {
    val iterator = List(1, 2, 3).iterator
    iterator.next must be_==(3).eventually
  }
  "A matcher can work with eventually and be_== but a type annotation is necessary or a be_=== matcher" in {
    val option: Option[Int] = Some(3)
    option must be_==(Some(3)).eventually
  }

Answer 5

我花了一段时间才找到这个所以我想分享一下。我应该阅读发行说明。在 specs2 v3.5 中，需要使用隐式 ExecutionEnv 才能使用 await for future。这也可以用于未来的转换（即地图）见http://notes.implicit.ly/post/116619383574/specs2-3-5。

从那里摘录以供快速参考：

import org.specs2.concurrent.ExecutionEnv

class MySpec extends mutable.Specification {
  "test of a Scala Future" >> { implicit ee: ExecutionEnv =>
    Future(1) must be_>(0).await
  }
}

Answer 6

等待是一种反模式。永远不应该使用它。您可以使用 ScalaFutures、IntegrationPatience 和 Eventually.

等特征

whenReady 提供您正在寻找的魔法。

示例：

import org.specs2.mutable.Specification
import scala.concurrent.ExecutionContext.Implicits.global
import scala.util.{Failure, Success}
import org.scalatest.concurrent.{IntegrationPatience, ScalaFutures}
import scala.concurrent.Future

class AsyncWebClientSpec extends Specification
    with ScalaFutures
    with IntegrationPatience {

    "WebClient when downloading images" should {

        "for a valid link return non-zero content " in {

            whenReady(Future.successful("Done")){ testImage =>

                testImage must be equalTo "Done"           
                // Do whatever you need
            }

        }
    }
}

如何测试return Future 的方法？

How to test methods that return Future?

scala

specs2