Scalatest: run each test N times using a command-line argument

Repeated.scala

import org.scalatest._

sealed trait Repeated extends TestSuiteMixin { this: TestSuite =>
  protected abstract override def runTest(testName: String, args: Args): Status = {
    def run0(times: Int): Status = {
      val status = super.runTest(testName, args)
      if (times <= 1) status else status.thenRun(run0(times - 1))
    }

    run0(args.configMap.getWithDefault("times", "1").toInt)
  }
}

// sample usage:

class SomeTest extends FunSuite with Matchers with Repeated {
  test("sometimes fails") {
    scala.util.Random.nextDouble() shouldBe > (0.05d) // 5% chance to fail
  }
}


/*

$ sbt "test-only SomeTest -- -Dtimes=20"
[info] SomeTest:
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails
[info] - sometimes fails *** FAILED ***
[info]   0.012614120654887317 was not greater than 0.05 (Repeated.scala:19)
[info] - sometimes fails
[info] - sometimes fails *** FAILED ***
[info]   0.022310937247545737 was not greater than 0.05 (Repeated.scala:19)
[info] - sometimes fails
[info] - sometimes fails
[info] Run completed in 365 milliseconds.
[info] Total number of tests run: 20
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 18, failed 2, canceled 0, ignored 0, pending 0
[info] *** 2 TESTS FAILED ***
[error] Failed tests:
[error] 	SomeTest
[error] (test:testOnly) sbt.TestsFailedException: Tests unsuccessful
[error] Total time: 1 s, completed Feb 16, 2017 10:28:48 AM

 */