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Unit Testing Futures With ScalaTest

Unit testing methods that return futures in Scala is quite straightforward using ScalaTest 2.0+

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import org.scalatest.FunSuite
import org.scalatest.concurrent.ScalaFutures
import scala.concurrent.Future

class NiceClass$Test extends FunSuite with ScalaFutures {
  test("Test a method that returns a future") {
    val f: Future[Boolean] = somethingThatReturnsAFuture()

    whenReady(f) { result =>
      assert(result)
    }
  }
}

If your future is making a web service call or doing some sort of IO that takes a few seconds to complete, you might encounter an error like this one:

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A timeout occurred waiting for a future to complete.
Queried 11 times, sleeping 15 milliseconds between each query.

You can fix this by telling ScalaFutures how long it should to wait before declaring that the future has timed out.

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import org.scalatest.time.{Millis, Seconds, Span}

implicit val defaultPatience =
  PatienceConfig(timeout = Span(5, Seconds), interval = Span(500, Millis))

Happy testing!