ScalaTest：在失败的期货中断言异常（非阻塞）

Question

import org.scalatest.{ FlatSpec, Matchers, ParallelTestExecution }
import org.scalatest.concurrent.ScalaFutures
import org.apache.thrift.TApplicationException

class Test extends FlatSpec with Matchers with ScalaFutures with ParallelTestExecution {
  it should "throw org.apache.thrift.TApplicationException for invalid Ids" in {
    val future: Future[Response] = ThriftClient.thriftRequest
    whenReady(future) {
      res => {
       intercept[TApplicationException] {
       }
      }
    }
  }
}

问题：如何在 Futures 中断言预期的失败而不阻塞？以上不起作用，在intercept块之前抛出异常。

Answer 1

我知道这可能有点晚了，但是 ScalaTest 通过混合 ScalaFutures 特征或直接在您的测试函数中使用它，开箱即用地提供了这个功能（我相信从版本 2 开始）。看！

test("some test") {
  val f: Future[Something] = someObject.giveMeAFuture
  ScalaFutures.whenReady(f.failed) { e =>
    e shouldBe a [SomeExceptionType]
  }
}

或者您可以在其中执行一些其他断言。基本上，如果你的未来没有像你预期的那样失败，那么测试就会失败。如果失败，但抛出了不同的异常，则测试将失败。好，易于！ =]

---

厚颜无耻的编辑：

你也可以使用这个方法来测试任何返回未来的东西：

test("some test") {
  val f: Future[Something] = someObject.giveMeAFuture
  ScalaFutures.whenReady(f) { s =>
    // run assertions against the object returned in the future
  }
}

---

最近的编辑！

我只是想根据更新版本的 Scala 测试用更多有用的信息来更新这个答案。各种规格特征现在都具有异步支持，因此不要扩展 WordSpec，而是扩展 AsyncWordSpec，而不是像上面那样依赖 whenReady 调用，你只需直接映射你的期货在测试中。

例子：

class SomeSpec extends Async[*]Spec with Matchers {

...

  test("some test") {
    someObject.funcThatReturnsAFutureOfSomething map { something =>
      // run assertions against the 'something' returned in the future
    }
  }
}

Answer 2

这也隐藏在评论中，但 Scalatest 的 FutureValues mixin 已经涵盖了您。

只需使用f.failed.futureValue shouldBe an[TApplicationException]

Answer 3

注意：留下这个答案是因为 OP 发现它很有帮助，但对于 Scala Futures，请参阅另一个答案。

这有点样板，但Waiter来自AsyncAssertions：

import org.scalatest.{ FlatSpec, Matchers, ParallelTestExecution }
import org.scalatest.concurrent.{ ScalaFutures, AsyncAssertions, PatienceConfiguration }
import concurrent.Future
import concurrent.ExecutionContext.Implicits._
import util._ 

class Test extends FlatSpec with Matchers with ScalaFutures with ParallelTestExecution with AsyncAssertions {
  it should "throw for invalid Ids" in {
    val f: Future[Int] = new Goof().goof
    val w = new Waiter
    f onComplete {
      case Failure(e) => w(throw e); w.dismiss()
      case Success(_) => w.dismiss()
    }
    intercept[UnsupportedOperationException] {
      w.await
    }
  }
}

给定

import concurrent.Future
import concurrent.ExecutionContext.Implicits._

class Goof {
  def goof(delay: Int = 1): Future[Int] = Future {
    Thread sleep delay * 1000L
    throw new UnsupportedOperationException
  } 
  def goofy(delay: Int = 1): Future[Int] = Future {
    Thread sleep delay * 1000L
    throw new NullPointerException
  } 
  def foog(delay: Int = 1): Future[Int] = Future {
    Thread sleep delay * 1000L
    7
  }
}

换句话说，

class Test extends FlatSpec with Matchers with ScalaFutures with ParallelTestExecution with AsyncAssertions {
  it should "throw for invalid Ids" in {
    val f: Future[Int] = new Goof().goof
    import Helper._
    f.failing[UnsupportedOperationException] 
  }
}

object Helper {
  implicit class Failing[A](val f: Future[A]) extends Assertions with AsyncAssertions {
    def failing[T <: Throwable](implicit m: Manifest[T]) = {
      val w = new Waiter
      f onComplete {
        case Failure(e) => w(throw e); w.dismiss()
        case Success(_) => w.dismiss()
      }
      intercept[T] {
        w.await
      }
    } 
  } 
} 

或者，如果您有多个期货，并且您希望第一个不合格的期货未能通过测试：

trait FailHelper extends Assertions with AsyncAssertions with PatienceConfiguration {
  def failingWith[T <: Throwable : Manifest](fs: Future[_]*)(implicit p: PatienceConfig) {
    val count = new java.util.concurrent.atomic.AtomicInteger(fs.size)
    val w = new Waiter
    for (f <- fs) f onComplete {
      case Success(i) =>
        w(intercept[T](i))
        println(s"Bad success $i")
        w.dismiss()
      case Failure(e: T) =>
        println(s"Failed $e OK, count ${count.get}")
        w(intercept[T](throw e))
        if (count.decrementAndGet == 0) w.dismiss()
      case Failure(e) =>
        println(s"Failed $e Bad")
        w(intercept[T](throw e))
        w.dismiss()
    }
    w.await()(p)
  }
}

有用法

class Test extends FlatSpec with Matchers with ScalaFutures with ParallelTestExecution with FailHelper {
  it should "throw for invalid Ids" in {
    val sut = new Goof()
    import sut._

    val patienceConfig = null  // shadow the implicit
    implicit val p = PatienceConfig(timeout = 10 seconds)

    // all should fail this way
    //failingWith[UnsupportedOperationException](goof(), goofy(3), foog(5))
    //failingWith[UnsupportedOperationException](goof(), foog(5))
    failingWith[UnsupportedOperationException](goof(), goof(2), goof(3))
  }
}

灵感来自this unloved answer。

Answer 4

ScalaTest 3.0 添加async versions of the spec traits 和AsyncFreeSpec 一样：

import org.scalatest.{AsyncFlatSpec, Matchers}
import scala.concurrent.Future

class ScratchSpec extends AsyncFlatSpec with Matchers  {

    def thriftRequest = Future { throw new Exception() }

    it should "throw exception" in {
        recoverToSucceededIf[Exception] {
            thriftRequest
        }
    }
}

Answer 5

除了Brian Low 的回答，我还为recoverToSucceededIf 找到了一个很好的解释。这适用于所有 Async 样式（来自 ScalaTest 3）：

可以通过两种方式测试失败的期货：使用recoverToSucceededIf 或recoverToExceptionIf

• recoverToSucceededIf 用于断言未来结束的异常类型：

"return UserNotFoundException" when {
       "the user does not exist" in {
         recoverToSucceededIf[UserNotFoundException](userService.findUser("1"))
       }
     }

• recoverToExceptionIf 在您想要测试某些异常字段时很有用：

"return UserAlreadyExistsException" when {
     "adding a user with existing username" in {
       recoverToExceptionIf[UserAlreadyExistsException] {
         userService.addUser(user)
       }.map { ex =>
         ex.message shouldBe s"User with username: $username already exists!"
       }
     }
   } 

查看Tudor Zgureanu — What's new in ScalaTest 3的整个博客

Answer 6

你也可以试试这个简单而简短的东西

test("some test throwing SQL Exception") {
      val f: Future[Something] = someObject.giveMeAFuture
      recoverToSucceededIf[SQLException](f)
    }