ScaledTimeSpans

Trait providing a scaled method that can be used to scale time Spans used during the testing of asynchronous operations.

The scaled method allows tests of asynchronous operations to be tuned according to need. For example, Spans can be scaled larger when running tests on slower continuous integration servers or smaller when running on faster development machines.

The Double factor by which to scale the Spans passed to scaled is obtained from the spanScaleFactor method, also declared in this trait. By default this method returns 1.0, but can be configured to return a different value by passing a -F argument to Runner (or an equivalent mechanism in an ant, sbt, or Maven build file).

The default timeouts and intervals defined for traits Eventually and Waiters invoke scaled, so those defaults will be scaled automatically. Other than such defaults, however, to get a Span to scale you'll need to explicitly pass it to scaled. For example, here's how you would scale a Span you supply to the failAfter method from trait Timeouts:

failAfter(scaled(150 millis)) {
 // ...
}

The reason Spans are not scaled automatically in the general case is to make code obvious. If a reader sees failAfter(1 second), it will mean exactly that: fail after one second. And if a Span will be scaled, the reader will clearly see that as well: failAfter(scaled(1 second)).

== Overriding spanScaleFactor ==

You can override the spanScaleFactor method to configure the factor by a different means. For example, to configure the factor from Akka TestKit's test time factor you might create a trait like this:

import org.scalatest.concurrent.ScaledTimeSpans
import akka.actor.ActorSystem
import akka.testkit.TestKitExtension

trait AkkaSpanScaleFactor extends ScaledTimeSpans {
 override def spanScaleFactor: Double =
     TestKitExtension.get(ActorSystem()).TestTimeFactor
}

This trait overrides spanScaleFactor so that it takes its scale factor from Akka's application.conf file. You could then scale Spans tenfold in Akka's configuration file like this:

akka {
 test {
   timefactor = 10.0
 }
}

Armed with this trait and configuration file, you can simply mix trait AkkaSpanScaleFactor into any test class whose Spans you want to scale, like this:

class MySpec extends FunSpec with Eventually with AkkaSpanScaleFactor {
 // ..
}