Scopes

Scope

The techniques described in Context objects are not always applicable to unit specifications where we want examples to be a “block” of code described by some text. Instead of creating a case class we can instantiate a trait which will hold a “fresh” state:

class ContextSpec extends mutable.Specification {
  "this is the first example" in new trees {
    tree.removeNodes(2, 3) must have size(2)
  }
  "this is the first example" in new trees {
    tree.removeNodes(2, 3, 4) must have size(1)
  }
}

/** the `trees` context */
trait trees extends Scope {
  val tree = new Tree(1, 2, 3, 4)
}

Each example of that specification gets a new instance of the trees trait. So it will have a brand new tree variable and even if this data is mutated by an example, other examples will be isolated from these changes.

Now you might wonder why the trees trait is extending the org.specs2.specification.Scope trait? The reason is that the body of an Example only accepts objects which are convertible to a Result. By extending Scope we can take advantage of an implicit conversion provided by the Specification trait to convert our context object to a Result.

Before / After

It is also possible to extend Scopes with Before and After traits but they need to be org.specs2.mutable.Before and org.specs2.mutable.After traits. This is necessary because those traits extend the Scala DelayedInit trait allowing to insert code around the execution of the body of an object.

And if you want to know more