Waiters

A configuration parameter that specifies the number of dismissals to wait for before returning normally from an await call on a Waiter.

Configuration object for asynchronous constructs, such as those provided by traits Eventually and Waiters.

The default values for the parameters are:

Configuration Parameter	Default Value
timeout	scaled(150 milliseconds)
interval	scaled(15 milliseconds)

Class that facilitates performing assertions outside the main test thread, such as assertions in callback methods that are invoked asynchronously.

To use Waiter, create an instance of it in the main test thread:

val w = new Waiter // Do this in the main test thread

At some point later, call await on the waiter:

w.await() // Call await() from the main test thread

The await call will block until it either receives a report of a failed assertion from a different thread, at which point it will complete abruptly with the same exception, or until it is dismissed by a different thread (or threads), at which point it will return normally. You can optionally specify a timeout and/or a number of dismissals to wait for. Here's an example:

import org.scalatest.time.SpanSugar._

w.await(timeout(300 millis), dismissals(2))

The default value for timeout, provided via an implicit PatienceConfig parameter, is 150 milliseconds. The default value for dismissals is 1. The await method will block until either it is dismissed a sufficient number of times by other threads or an assertion fails in another thread. Thus if you just want to perform assertions in just one other thread, only that thread will be performing a dismissal, so you can use the default value of 1 for dismissals.

Waiter contains four overloaded forms of await, two of which take an implicit PatienceConfig parameter. To change the default timeout configuration, override or hide (if you imported the members of Waiters companion object instead of mixing in the trait) patienceConfig with a new one that returns your desired configuration.

To dismiss a waiter, you just invoke dismiss on it:

w.dismiss() // Call this from one or more other threads

You may want to put dismiss invocations in a finally clause to ensure they happen even if an exception is thrown. Otherwise if a dismissal is missed because of a thrown exception, an await call will wait until it times out.

Finally, to perform an assertion in a different thread, you just apply the Waiter to the assertion code. Here are some examples:

w { assert(1 + 1 === 3) }    // Can use assertions
w { 1 + 1 should equal (3) } // Or matchers
w { "hi".charAt(-1) }        // Any exceptions will be forwarded to await

Here's a complete example:

import org.scalatest._
import concurrent.Waiters
import scala.actors.Actor

class ExampleSuite extends FunSuite with Matchers with Waiters {

 case class Message(text: String)

 class Publisher extends Actor {

   @volatile private var handle: Message => Unit = { (msg) => }

   def registerHandler(f: Message => Unit) {
     handle = f
   }

   def act() {
     var done = false
     while (!done) {
       react {
         case msg: Message => handle(msg)
         case "Exit" => done = true
       }
     }
   }
 }

 test("example one") {

   val publisher = new Publisher
   val message = new Message("hi")
   val w = new Waiter

   publisher.start()

   publisher.registerHandler { msg =>
     w { msg should equal (message) }
     w.dismiss()
   }

   publisher ! message
   w.await()
   publisher ! "Exit"
 }
}

Returns a Dismissals configuration parameter containing the passed value, which specifies the number of dismissals to wait for before returning normally from an await call on a Waiter.

Returns an Interval configuration parameter containing the passed value, which specifies the amount of time to sleep after a retry.

Scales the passed Span by the Double factor returned by spanScaleFactor.

The Span is scaled by invoking its scaledBy method, thus this method has the same behavior: The value returned by spanScaleFactor can be any positive number or zero, including a fractional number. A number greater than one will scale the Span up to a larger value. A fractional number will scale it down to a smaller value. A factor of 1.0 will cause the exact same Span to be returned. A factor of zero will cause Span.ZeroLength to be returned. If overflow occurs, Span.Max will be returned. If underflow occurs, Span.ZeroLength will be returned.

The factor by which the scaled method will scale Spans.

The default implementation of this method will return the span scale factor that was specified for the run, or 1.0 if no factor was specified. For example, you can specify a span scale factor when invoking ScalaTest via the command line by passing a -F argument to Runner.

Returns a Timeout configuration parameter containing the passed value, which specifies the maximum amount to wait for an asynchronous operation to complete.

Implicit PatienceConfig value providing default configuration values.

To change the default configuration, override or hide this def with another implicit PatienceConfig containing your desired default configuration values.