ParallelTestExecution causes sbt to think tests always pass.

build.properties

sbt.version=0.13.6

Build.scala

package org.acme.dummy

import sbt._
import sbt.Keys._


object DummyBuild extends Build {

  val coreProject = Project(
    id = "dummy",
    base = file("."),
    settings = Seq(
    name := "dummy",
    scalaVersion := "2.10.4",
    libraryDependencies ++= Seq(
      "org.scalatest" %% "scalatest" % "2.2.2" % "test"),
    parallelExecution in Test := true,
    concurrentRestrictions := Seq(Tags.limitAll(100))
    )
  )
}

DummySpec.scala

package org.acme.dummy

import org.scalatest.{Matchers, FlatSpec, ParallelTestExecution}

class DummySpec extends FlatSpec with Matchers with ParallelTestExecution {

  "numbers" should "add" in {
    (2 + 2) shouldBe 4
   }

  "numbers" should "negate" in {
    // Whoops, failing test
    2 - 2 shouldBe 1
  }

}