AsResult typeclass

There are many ways to define expectations in specs2:

• Boolean (true, false)
• Standard result (success, failure)
• Matcher result (1 must_== 1)
• Scalacheck property
• DataTable
• Forms

All of these types implement the org.specs2.execute.AsResult typeclass, meaning that they can be transformed into a Result:

trait AsResult[T] {
  def asResult(t: =>T): Result
}

This gives some flexibility in integrating any kind of custom definition of a “result” into specs2 and this is why you find this typeclass as a requirement to build examples or to declare contexts. You can take advantage of this type class by defining your own kind of result and providing a typeclass instance for it:

// A new type of results for cluster execution
trait ClusterExecution {
  def succeeded: Boolean
  def errorMessage: String
}

object ClusterExecution {
  implicit def clusterExecutionAsResult: AsResult[ClusterExecution] =
    new AsResult[ClusterExecution] {
      def asResult(t: =>ClusterExecution): Result = {
        try {
          val result = t
          if (result.succeeded) Success()
          else                  Failure(t.errorMessage)
        } catch { case e: Throwable => Error(e) }
      }
   }
}

Decorated results

You can also embed custom data in a special kind of Result, a DecoratedResult:

case class DecoratedResult[+T](decorator: T, result: Result) extends Result(result.message, result.expected)

A DecoratedResult[T] decorates an ordinary result with an additional value of type T. If you want to take advantage of this custom value in your reports you will need to build a custom org.specs2.reporter.Printer, probably extending an existing one.

And if you want to know more