ScalaTest: Assert exceptions in failed futures (non-blocking)

Question

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

class         


        

Answer 1

Note: leaving this answer because the OP found it helpful, but for Scala Futures see the other answer.

This is a bit boilerplated, but Waiter from 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
    }
  }
}

given

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
  }
}

In other words,

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
      }
    } 
  } 
} 

Or, if you have multiple futures and you want the first non-conforming future to fail the test:

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)
  }
}

with usage

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))
  }
}

Inspired by this unloved answer.