ScalaTest_Futures.scala

import org.scalatest.{Assertion, AsyncFlatSpec}
import scala.concurrent.{Future, Await}
import org.scalatest.Matchers._
import scala.concurrent.duration._
import scala.language.postfixOps

class FutureSpec extends AsyncFlatSpec {

  // Overriding execution context is not required, unless you want to use Await.
  // To avoid deadlocking the main thread you need to have multithreaded context.
  implicit override val executionContext = scala.concurrent.ExecutionContext.Implicits.global

  def assertAll(futures: Future[Assertion]*): Future[Assertion] =
    Future.sequence(futures) map (_.foreach(a => a)) map (_ => succeed)
  
  "non-future assertions" should "be all checked as expected" in {
    1 shouldEqual 2 // fails here
    2 shouldEqual 2
  }

  "all future assertions" should "be checked BUT this test doesn't fail" in {
    Future { 1 shouldEqual 2 } // doesn't fail here as expected
    Future { 2 shouldEqual 2 }
  }
  
  "all future assertions" should "be checked BUT this test checks only last one" in {
    Future { 1 shouldEqual 2 } // doesn't fail here as expected
    Future { 3 shouldEqual 4 } // only last Future[Assertion] is checked
  }

  "all future assertions" should "be checked with our helper and this test fails as it should" in {
    val a1 = Future { 1 shouldEqual 2 }
    // you can do more things here
    val a2 = Future { 2 shouldEqual 2 }

    assertAll(a1, a2)
  }
  
  "all future assertions" should "be checked with Await, but this introduces blocking" in {
    Await.result(Future { 1 shouldEqual 2 }, 2 seconds)
    Await.result(Future { 2 shouldEqual 2 }, 2 seconds)
  }
}

(new FutureSpec).execute(color = false, shortstacks = true)

testOnly *FutureSpec
[info] Compiling 1 Scala source to ...
[info] Done compiling.
[info] FutureSpec:
[info] non-future assertions
[info] - should be all checked as expected *** FAILED ***
[info] 1 did not equal 2 (FutureSpec.scala:122)
[info] all future assertions
[info] - should be checked BUT this test doesn't fail
[info] all future assertions
[info] - should be checked BUT this test checks only last one *** FAILED ***
[info] 3 did not equal 4 (FutureSpec.scala:133)
[info] all future assertions
[info] all future assertions
[info] - should be checked with our helper and this test fails as it should *** FAILED ***
[info] 1 did not equal 2 (FutureSpec.scala:137)
[info] - should be checked with Await, but this introduces blocking *** FAILED ***
[info] 1 did not equal 2 (FutureSpec.scala:145)
[info] Run completed in 885 milliseconds.
[info] Total number of tests run: 5
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 1, failed 4, canceled 0, ignored 0, pending 0
[info] *** 4 TESTS FAILED ***
[error] Failed tests:
[error] FutureSpec
[error] (Test / testOnly) sbt.TestsFailedException: Tests unsuccessful