scalatestCoreDotty/org.scalatest.concurrent/ScalaFutures

ScalaFutures

Provides an implicit conversion from scala.concurrent.Future[T] to FutureConcept[T].

This trait enables you to invoke the methods defined on FutureConcept on a Scala Future, as well as to pass a Scala future to the whenReady methods of supertrait Futures. The three ways this trait enables you to test futures are:

Invoking isReadyWithin, to assert that a future is ready within a a specified time period. Here's an example:

assert(result.isReadyWithin(100 millis))

Invoking futureValue, to obtain a futures result within a specified or implicit time period, like this:

assert(result.futureValue === 7)

// Or, if you expect the future to fail:
assert(result.failed.futureValue.isInstanceOf[ArithmeticException])

Passing the future to whenReady, and performing assertions on the result value passed to the given function, as in:

whenReady(result) { s =>
 s should be ("hello")
}

The whenReady construct periodically inspects the passed future, until it is either ready or the configured timeout has been surpassed. If the future becomes ready before the timeout, whenReady passes the future's value to the specified function.

To make whenReady more broadly applicable, the type of future it accepts is a FutureConcept[T], where T is the type of value promised by the future. Passing a future to whenReady requires an implicit conversion from the type of future you wish to pass (the modeled type) to FutureConcept[T]. Subtrait JavaFutures provides an implicit conversion from java.util.concurrent.Future[T] to FutureConcept[T].

For example, the following invocation of whenReady would succeed (not throw an exception):

import org.scalatest._
import Matchers._
import concurrent.Futures._
import java.util.concurrent._

val exec = Executors.newSingleThreadExecutor
val task = new Callable[String] { def call() = { Thread.sleep(50); "hi" } }
whenReady(exec.submit(task)) { s =>
 s should be ("hi")
}

However, because the default timeout is 150 milliseconds, the following invocation of whenReady would ultimately produce a TestFailedException:

val task = new Callable[String] { def call() = { Thread.sleep(500); "hi" } }
whenReady(exec.submit(task)) { s =>
 s should be ("hi")
}

Assuming the default configuration parameters, a timeout of 150 milliseconds and an interval of 15 milliseconds, were passed implicitly to whenReady, the detail message of the thrown TestFailedException would look like:

The future passed to whenReady was never ready, so whenReady timed out. Queried 95 times, sleeping 10 milliseconds between each query.

== Configuration of whenReady ==

The whenReady methods of this trait can be flexibly configured. The two configuration parameters for whenReady along with their default values and meanings are described in the following table:

Configuration Parameter	Default Value	Meaning
timeout	scaled(150 milliseconds)	the maximum amount of time to allow unsuccessful queries before giving up and throwing `TestFailedException`
interval	scaled(15 milliseconds)	the amount of time to sleep between each query

The default values of both timeout and interval are passed to the scaled method, inherited from ScaledTimeSpans, so that the defaults can be scaled up or down together with other scaled time spans. See the documentation for trait ScaledTimeSpans for more information.

The whenReady methods of trait Futures each take a PatienceConfig object as an implicit parameter. This object provides values for the two configuration parameters. Trait Futures provides an implicit val named defaultPatience with each configuration parameter set to its default value. If you want to set one or more configuration parameters to a different value for all invocations of whenReady in a suite you can override this val (or hide it, for example, if you are importing the members of the Futures companion object rather than mixing in the trait). For example, if you always want the default timeout to be 2 seconds and the default interval to be 5 milliseconds, you can override defaultPatience, like this:

implicit override val defaultPatience =
 PatienceConfig(timeout = Span(2, Seconds), interval = Span(5, Millis))

Or, hide it by declaring a variable of the same name in whatever scope you want the changed values to be in effect:

implicit val defaultPatience =
 PatienceConfig(timeout =  Span(2, Seconds), interval = Span(5, Millis))

In addition to taking a PatienceConfig object as an implicit parameter, the whenReady methods of trait Futures include overloaded forms that take one or two PatienceConfigParam objects that you can use to override the values provided by the implicit PatienceConfig for a single whenReady invocation. For example, if you want to set timeout to 6 seconds for just one particular whenReady invocation, you can do so like this:

whenReady (exec.submit(task), timeout(Span(6, Seconds))) { s =>
 s should be ("hi")
}

This invocation of eventually will use 6000 for timeout and whatever value is specified by the implicitly passed PatienceConfig object for the interval configuration parameter. If you want to set both configuration parameters in this way, just list them separated by commas:

whenReady (exec.submit(task), timeout(Span(6, Seconds)), interval(Span(500, Millis))) { s =>
 s should be ("hi")
}

You can also import or mix in the members of SpanSugar if you want a more concise DSL for expressing time spans:

whenReady (exec.submit(task), timeout(6 seconds), interval(500 millis)) { s =>
 s should be ("hi")
}

Note: The whenReady construct was in part inspired by the whenDelivered matcher of the BlueEyes project, a lightweight, asynchronous web framework for Scala.

Companion:: object

trait Futures

trait PatienceConfiguration

trait AbstractPatienceConfiguration

trait ScaledTimeSpans

class Object

trait Matchable

class Any

object ScalaFutures.type

Type members

Inherited classlikes

Concept trait for futures, instances of which are passed to the whenReady methods of trait Futures.

See the documentation for trait Futures for the details on the syntax this trait provides for testing with futures.

Inherited from:: Futures

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)`

Value parameters:

interval: the amount of time to sleep between each check of the status of an asynchronous operation when polling
timeout: the maximum amount of time to wait for an asynchronous operation to complete before giving up and throwing TestFailedException.

Inherited from:

AbstractPatienceConfiguration

Value members

Inherited methods

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

Inherited from:: PatienceConfiguration

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.

Throws:

IllegalArgumentException: if the value returned from spanScaleFactor is less than zero

Inherited from:

ScaledTimeSpans

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.

Inherited from:: ScaledTimeSpans

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

Inherited from:: PatienceConfiguration

Queries the passed future repeatedly until it either is ready, or a configured maximum amount of time has passed, sleeping a configured interval between attempts; and when ready, passes the future's value to the passed function.

The maximum amount of time in milliseconds to tolerate unsuccessful attempts before giving up is configured by the timeout field of the PatienceConfig passed implicitly as the last parameter. The interval to sleep between attempts is configured by the interval field of the PatienceConfig passed implicitly as the last parameter.

If the eitherValue method of the underlying Scala future returns a scala.Some containing a scala.util.Failure containing a java.util.concurrent.ExecutionException, and this exception contains a non-null cause, that cause will be included in the TestFailedException as its cause. The ExecutionException will be be included as the TestFailedException's cause only if the ExecutionException's cause is null.

Value parameters:

config: an PatienceConfig object containing timeout and interval parameters that are unused by this method
fun: the function to which pass the future's value when it is ready
future: the future to query

Returns:

the result of invoking the fun parameter

Inherited from:

Futures

The maximum amount of time in milliseconds to tolerate unsuccessful attempts before giving up is configured by the timeout field of the PatienceConfig passed implicitly as the last parameter. The interval to sleep between attempts is configured by the value contained in the passed interval parameter.

Value parameters:

config: an PatienceConfig object containing timeout and interval parameters that are unused by this method
fun: the function to which pass the future's value when it is ready
future: the future to query
interval: the Interval configuration parameter

Returns:

the result of invoking the fun parameter

Inherited from:

Futures

The maximum amount of time in milliseconds to tolerate unsuccessful queries before giving up and throwing TestFailedException is configured by the value contained in the passed timeout parameter. The interval to sleep between attempts is configured by the interval field of the PatienceConfig passed implicitly as the last parameter.

Value parameters:

config: an PatienceConfig object containing timeout and interval parameters that are unused by this method
fun: the function to which pass the future's value when it is ready
future: the future to query
timeout: the Timeout configuration parameter

Returns:

the result of invoking the fun parameter

Inherited from:

Futures

The maximum amount of time to tolerate unsuccessful queries before giving up and throwing TestFailedException is configured by the value contained in the passed timeout parameter. The interval to sleep between attempts is configured by the value contained in the passed interval parameter.

Value parameters:

config: an PatienceConfig object containing timeout and interval parameters that are unused by this method
fun: the function to which pass the future's value when it is ready
future: the future to query
interval: the Interval configuration parameter
timeout: the Timeout configuration parameter

Returns:

the result of invoking the fun parameter

Inherited from:

Futures

Implicits

Implicitly converts a scala.concurrent.Future[T] to FutureConcept[T], allowing you to invoke the methods defined on FutureConcept on a Scala Future, as well as to pass a Scala future to the whenReady methods of supertrait Futures.

See the documentation for supertrait Futures for the details on the syntax this trait provides for testing with Java futures.

The isExpired method of the returned FutureConcept will always return false, because the underlying type, scala.concurrent.Future, does not support the notion of expiration. Likewise, the isCanceled method of the returned FutureConcept will always return false, because the underlying type, scala.concurrent.Future, does not support the notion of cancelation.

Value parameters:

scalaFuture: a scala.concurrent.Future[T] to convert

Returns:

a FutureConcept[T] wrapping the passed scala.concurrent.Future[T]

Inherited implicits

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.

Inherited from:: PatienceConfiguration