Execution environment

When you run a specification, a java.util.concurrent.ExecutorService is used to execute examples concurrently. You can access this ExecutorService to execute futures (from Scala, Scalaz etc…), by converting it to the kind of “Execution context” required by your Future implementation.

Scala Future

A Scala Future needs an implicit ExecutionContext to be created. You can get an execution context, out of the box, shared across all specifications by declaring it as a class member:

class MyFutureSpec(using ec: ExecutionContext) extends Specification:
  def is = s2"""
    Let's check this scala future ${Await.result(Future(1), Duration.Inf) must ===(1)}
  """

// in a mutable specification
class MyMutableFutureSpec(using ec: ExecutionContext) extends mutable.Specification:
  "Let's check this scala future" >> {
    Await.result(Future(1), Duration.Inf) must ===(1)
  }

You can also use an ExecutionEnv (from now on code examples are provided for immutable specifications only but are transposable to mutable ones):

class MyFutureSpec(using ee: ExecutionEnv) extends Specification:
  def is = s2"""
    Let's check this scala future ${Await.result(Future(1), Duration.Inf) must ===(1)}
  """

This works thanks to an implicit conversion between ExecutionEnv and ExecutionContext provided by the org.specs2.execute.ImplicitExecutionContextFromExecutionEnv trait (this can be deactivated by mixing-in the NoImplicitExecutionContextFromExecutionEnv trait).

It is actually better to use an ExecutionEnv anyway because it is required when you want to create Future matchers (see the “Future” tab). Indeed an ExecutionEnv contains a timeFactor which can be used to modify the timeout from the command line and wait longer for Futures executing on a continuous integration server for example.

With matchers

Future Matchers (see the “Future” tab) require an implicit ExecutionEnv. This environment is used to access the timeFactor when awaiting for Scala Futures.

The terminate matcher (see the “Termination” tab in the optional Matchers section) also needs an ExecutionEnv to run a piece of code and periodically check if it has terminated or not:

s2"""
  this code must be fast enough ${
      given ExecutionEnv = ExecutionEnv.fromGlobalExecutionContext
      Thread.sleep(100) must terminate(retries = 1, sleep = 60.millis)
  }
"""

One per specification

If you want to have exactly one Env or one ExecutionEnv per Specification you can mix-in the org.specs2.specicication.core.OwnEnv or the org.specs2.specicication.core.OwnExecutionEnv traits. You will then get a specific thread pool instantiated and shutdown just for the execution of one specification. See the environment page for more information.

And if you want to know more