Flaky test result for ExampleSpec

ExampleSpec

A Stack should fail randomly often

12: 0 was equal to 0

Failed 1 times

Test run 12

Exception: org.scalatest.exceptions.TestFailedException

Message: 0 was equal to 0

org.scalatest.exceptions.TestFailedException: 0 was equal to 0
	at org.scalatest.MatchersHelper$.indicateFailure(MatchersHelper.scala:340)
	at org.scalatest.words.ResultOfNotWordForAny.be(ResultOfNotWordForAny.scala:85)
	at ExampleSpec.$anonfun$new$5(ExampleSpec.scala:29)
	at org.scalatest.OutcomeOf.outcomeOf(OutcomeOf.scala:85)
	at org.scalatest.OutcomeOf.outcomeOf$(OutcomeOf.scala:83)
	at org.scalatest.OutcomeOf$.outcomeOf(OutcomeOf.scala:104)
	at org.scalatest.Transformer.apply(Transformer.scala:22)
	at org.scalatest.Transformer.apply(Transformer.scala:20)
	at org.scalatest.FlatSpecLike$$anon$1.apply(FlatSpecLike.scala:1682)
	at org.scalatest.TestSuite.withFixture(TestSuite.scala:196)
	at org.scalatest.TestSuite.withFixture$(TestSuite.scala:195)
	at org.scalatest.FlatSpec.withFixture(FlatSpec.scala:1685)
	at org.scalatest.FlatSpecLike.invokeWithFixture$1(FlatSpecLike.scala:1680)
	at org.scalatest.FlatSpecLike.$anonfun$runTest$1(FlatSpecLike.scala:1692)
	at org.scalatest.SuperEngine.runTestImpl(Engine.scala:289)
	at org.scalatest.FlatSpecLike.runTest(FlatSpecLike.scala:1692)
	at org.scalatest.FlatSpecLike.runTest$(FlatSpecLike.scala:1674)
	at org.scalatest.FlatSpec.runTest(FlatSpec.scala:1685)
	at org.scalatest.FlatSpecLike.$anonfun$runTests$1(FlatSpecLike.scala:1750)
	at org.scalatest.SuperEngine.$anonfun$runTestsInBranch$1(Engine.scala:396)
	at scala.collection.immutable.List.foreach(List.scala:389)
	at org.scalatest.SuperEngine.traverseSubNodes$1(Engine.scala:384)
	at org.scalatest.SuperEngine.runTestsInBranch(Engine.scala:373)
	at org.scalatest.SuperEngine.$anonfun$runTestsInBranch$1(Engine.scala:410)
	at scala.collection.immutable.List.foreach(List.scala:389)
	at org.scalatest.SuperEngine.traverseSubNodes$1(Engine.scala:384)
	at org.scalatest.SuperEngine.runTestsInBranch(Engine.scala:379)
	at org.scalatest.SuperEngine.runTestsImpl(Engine.scala:461)
	at org.scalatest.FlatSpecLike.runTests(FlatSpecLike.scala:1750)
	at org.scalatest.FlatSpecLike.runTests$(FlatSpecLike.scala:1749)
	at org.scalatest.FlatSpec.runTests(FlatSpec.scala:1685)
	at org.scalatest.Suite.run(Suite.scala:1147)
	at org.scalatest.Suite.run$(Suite.scala:1129)
	at org.scalatest.FlatSpec.org$scalatest$FlatSpecLike$$super$run(FlatSpec.scala:1685)
	at org.scalatest.FlatSpecLike.$anonfun$run$1(FlatSpecLike.scala:1795)
	at org.scalatest.SuperEngine.runImpl(Engine.scala:521)
	at org.scalatest.FlatSpecLike.run(FlatSpecLike.scala:1795)
	at org.scalatest.FlatSpecLike.run$(FlatSpecLike.scala:1793)
	at org.scalatest.FlatSpec.run(FlatSpec.scala:1685)
	at org.scalatest.tools.Framework.org$scalatest$tools$Framework$$runSuite(Framework.scala:314)
	at org.scalatest.tools.Framework$ScalaTestTask.execute(Framework.scala:507)
	at sbt.TestRunner.runTest$1(TestFramework.scala:98)
	at sbt.TestRunner.run(TestFramework.scala:109)
	at sbt.TestFramework$$anon$2$$anonfun$$lessinit$greater$1.$anonfun$apply$1(TestFramework.scala:254)
	at sbt.TestFramework$.sbt$TestFramework$$withContextLoader(TestFramework.scala:225)
	at sbt.TestFramework$$anon$2$$anonfun$$lessinit$greater$1.apply(TestFramework.scala:254)
	at sbt.TestFramework$$anon$2$$anonfun$$lessinit$greater$1.apply(TestFramework.scala:254)
	at sbt.TestFunction.apply(TestFramework.scala:263)
	at sbt.Tests$.$anonfun$toTask$1(Tests.scala:277)
	at sbt.std.Transform$$anon$3.$anonfun$apply$2(System.scala:44)
	at sbt.std.Transform$$anon$4.work(System.scala:64)
	at sbt.Execute.$anonfun$submit$2(Execute.scala:257)
	at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:17)
	at sbt.Execute.work(Execute.scala:266)
	at sbt.Execute.$anonfun$submit$1(Execute.scala:257)
	at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:167)
	at sbt.CompletionService$$anon$2.call(CompletionService.scala:32)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)