Waiters
Related Docs:
object Waiters
| package concurrent
A configuration parameter that specifies the number of dismissals to wait for before returning normally
from an await call on a Waiter.
A configuration parameter that specifies the number of dismissals to wait for before returning normally
from an await call on a Waiter.
the number of dismissals for which to wait
IllegalArgumentException if specified value is less than or equal to zero.
Configuration object for asynchronous constructs, such as those provided by traits Eventually and
Waiters.
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)
|
the maximum amount of time to wait for an asynchronous operation to complete before giving up and throwing
TestFailedException.
the amount of time to sleep between each check of the status of an asynchronous operation when polling
Class that facilitates performing assertions outside the main test thread, such as assertions in callback methods that are invoked asynchronously.
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 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.
Returns an Interval configuration parameter containing the passed value, which
specifies the amount of time to sleep after a retry.
Implicit PatienceConfig value providing default configuration values.
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.
Scales the passed Span by the Double factor returned
by spanScaleFactor.
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.
IllegalArgumentException if the value returned from spanScaleFactor
is less than zero
The factor by which the scaled method will scale Spans.
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.
Returns a Timeout configuration parameter containing the passed value, which
specifies the maximum amount to wait for an asynchronous operation to complete.
Trait that facilitates performing assertions outside the main test thread, such as assertions in callback methods that are invoked asynchronously.
Trait
Waitersprovides aWaiterclass that you can use to orchestrate the inter-thread communication required to perform assertions outside the main test thread, and a means to configure it.To use
Waiter, create an instance of it in the main test thread:At some point later, call
awaiton the waiter:The
awaitcall 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:The default value for
timeout, provided via an implicitPatienceConfigparameter, is 150 milliseconds. The default value fordismissalsis 1. Theawaitmethod 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 fordismissals.Waitercontains four overloaded forms ofawait, two of which take an implicitPatienceConfigparameter. To change the default timeout configuration, override or hide (if you imported the members ofWaiterscompanion object instead of mixing in the trait)patienceConfigwith a new one that returns your desired configuration.To dismiss a waiter, you just invoke
dismisson it:You may want to put
dismissinvocations 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, anawaitcall will wait until it times out.Note that if a
Waiterreceives more than the expected number of dismissals, it will not report this as an error: i.e., receiving greater than the number of expected dismissals without any failed assertion will simply cause the the test to complete, not to fail. The only way aWaiterwill cause a test to fail is if one of the asynchronous assertions to which it is applied fails.Finally, to perform an assertion in a different thread, you just apply the
Waiterto 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 awaitHere'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" } }