Scalaz Failure tester for ScalaTest

scalazTestHelpers.scala

import org.scalatest.Suite

import scalaz._
import Scalaz._
import org.scalatest.matchers._

/**
 * Helper matchers for hacking with Scalaz.
 */
trait ScalazTestHelpers { self: Suite =>


  case class HasScalazFailureMatcher[E](element: E) extends Matcher[ValidationNel[E, _]] {

    def apply(validation: ValidationNel[E, _]): MatchResult = {
      MatchResult(
        validation match {
          case Success(_) =>
            true
          case Failure(n: NonEmptyList[E]) =>
            n.list contains element
          case _ =>
            false
        },
        s"$validation did not contain a Failure element matching '$element'.",
        s"$validation contained a Failure element matching '$element', but should not have."
      )
    }

  }

  /**
   * Checks if a scalaz.ValidationNel contains a specific failure element
   * Usage:
   *  validationObj should haveFailure (someErrorMessageOrObject)
   *
   * Can also be used to test multiple elements:
   *  validationObj should (haveFailure (someErrorMessageOrObject) and
   *                       haveFailure (someOtherErrorMessageOrObject))
   *
   */
  def haveFailure[E](element: E) = HasScalazFailureMatcher[E](element)

}