EmptySet$ cannot be returned by resourceOffers()
resourceOffers() should return Seq
***
If you're unsure why you're getting above error read on.
Due to the nature of the syntax above problem might occur because:
1. This exception *might* occur in wrongly written multi-threaded tests.
 Please refer to Mockito FAQ on limitations of concurrency testing.
2. A spy is stubbed using when(spy.foo()).then() syntax. It is safer to stub spies - 
 - with doReturn|Throw() family of methods. More in javadocs for Mockito.spy() method.


      org.mockito.exceptions.misusing.WrongTypeOfReturnValue: 
EmptySet$ cannot be returned by resourceOffers()
resourceOffers() should return Seq
***
If you're unsure why you're getting above error read on.
Due to the nature of the syntax above problem might occur because:
1. This exception *might* occur in wrongly written multi-threaded tests.
   Please refer to Mockito FAQ on limitations of concurrency testing.
2. A spy is stubbed using when(spy.foo()).then() syntax. It is safer to stub spies - 
   - with doReturn|Throw() family of methods. More in javadocs for Mockito.spy() method.

      at org.apache.spark.scheduler.cluster.YarnSchedulerBackendSuite$$anonfun$1$$anonfun$apply$mcV$sp$1$$anonfun$apply$1$$anonfun$apply$mcVI$sp$1.apply(YarnSchedulerBackendSuite.scala:54)
      at org.apache.spark.scheduler.cluster.YarnSchedulerBackendSuite$$anonfun$1$$anonfun$apply$mcV$sp$1$$anonfun$apply$1$$anonfun$apply$mcVI$sp$1.apply(YarnSchedulerBackendSuite.scala:48)
      at scala.collection.Iterator$class.foreach(Iterator.scala:891)
      at scala.collection.AbstractIterator.foreach(Iterator.scala:1334)
      at scala.collection.IterableLike$class.foreach(IterableLike.scala:72)
      at scala.collection.AbstractIterable.foreach(Iterable.scala:54)
      at org.apache.spark.scheduler.cluster.YarnSchedulerBackendSuite$$anonfun$1$$anonfun$apply$mcV$sp$1$$anonfun$apply$1.apply$mcVI$sp(YarnSchedulerBackendSuite.scala:48)
      at scala.collection.immutable.Range.foreach$mVc$sp(Range.scala:160)
      at org.apache.spark.scheduler.cluster.YarnSchedulerBackendSuite$$anonfun$1$$anonfun$apply$mcV$sp$1.apply(YarnSchedulerBackendSuite.scala:47)
      at org.apache.spark.scheduler.cluster.YarnSchedulerBackendSuite$$anonfun$1$$anonfun$apply$mcV$sp$1.apply(YarnSchedulerBackendSuite.scala:46)
      at scala.collection.Iterator$class.foreach(Iterator.scala:891)
      at scala.collection.AbstractIterator.foreach(Iterator.scala:1334)
      at scala.collection.IterableLike$class.foreach(IterableLike.scala:72)
      at scala.collection.AbstractIterable.foreach(Iterable.scala:54)
      at org.apache.spark.scheduler.cluster.YarnSchedulerBackendSuite$$anonfun$1.apply$mcV$sp(YarnSchedulerBackendSuite.scala:46)
      at org.apache.spark.scheduler.cluster.YarnSchedulerBackendSuite$$anonfun$1.apply(YarnSchedulerBackendSuite.scala:35)
      at org.apache.spark.scheduler.cluster.YarnSchedulerBackendSuite$$anonfun$1.apply(YarnSchedulerBackendSuite.scala:35)
      at org.scalatest.OutcomeOf$class.outcomeOf(OutcomeOf.scala:85)
      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.FunSuiteLike$$anon$1.apply(FunSuiteLike.scala:186)
      at org.apache.spark.SparkFunSuite.withFixture(SparkFunSuite.scala:104)
      at org.scalatest.FunSuiteLike$class.invokeWithFixture$1(FunSuiteLike.scala:183)
      at org.scalatest.FunSuiteLike$$anonfun$runTest$1.apply(FunSuiteLike.scala:196)
      at org.scalatest.FunSuiteLike$$anonfun$runTest$1.apply(FunSuiteLike.scala:196)
      at org.scalatest.SuperEngine.runTestImpl(Engine.scala:289)
      at org.scalatest.FunSuiteLike$class.runTest(FunSuiteLike.scala:196)
      at org.apache.spark.scheduler.cluster.YarnSchedulerBackendSuite.org$scalatest$BeforeAndAfterEach$$super$runTest(YarnSchedulerBackendSuite.scala:33)
      at org.scalatest.BeforeAndAfterEach$class.runTest(BeforeAndAfterEach.scala:221)
      at org.apache.spark.scheduler.cluster.YarnSchedulerBackendSuite.runTest(YarnSchedulerBackendSuite.scala:33)
      at org.scalatest.FunSuiteLike$$anonfun$runTests$1.apply(FunSuiteLike.scala:229)
      at org.scalatest.FunSuiteLike$$anonfun$runTests$1.apply(FunSuiteLike.scala:229)
      at org.scalatest.SuperEngine$$anonfun$traverseSubNodes$1$1.apply(Engine.scala:396)
      at org.scalatest.SuperEngine$$anonfun$traverseSubNodes$1$1.apply(Engine.scala:384)
      at scala.collection.immutable.List.foreach(List.scala:392)
      at org.scalatest.SuperEngine.traverseSubNodes$1(Engine.scala:384)
      at org.scalatest.SuperEngine.org$scalatest$SuperEngine$$runTestsInBranch(Engine.scala:379)
      at org.scalatest.SuperEngine.runTestsImpl(Engine.scala:461)
      at org.scalatest.FunSuiteLike$class.runTests(FunSuiteLike.scala:229)
      at org.scalatest.FunSuite.runTests(FunSuite.scala:1560)
      at org.scalatest.Suite$class.run(Suite.scala:1147)
      at org.scalatest.FunSuite.org$scalatest$FunSuiteLike$$super$run(FunSuite.scala:1560)
      at org.scalatest.FunSuiteLike$$anonfun$run$1.apply(FunSuiteLike.scala:233)
      at org.scalatest.FunSuiteLike$$anonfun$run$1.apply(FunSuiteLike.scala:233)
      at org.scalatest.SuperEngine.runImpl(Engine.scala:521)
      at org.scalatest.FunSuiteLike$class.run(FunSuiteLike.scala:233)
      at org.apache.spark.SparkFunSuite.org$scalatest$BeforeAndAfterAll$$super$run(SparkFunSuite.scala:53)
      at org.scalatest.BeforeAndAfterAll$class.liftedTree1$1(BeforeAndAfterAll.scala:213)
      at org.scalatest.BeforeAndAfterAll$class.run(BeforeAndAfterAll.scala:210)
      at org.apache.spark.SparkFunSuite.run(SparkFunSuite.scala:53)
      at org.scalatest.Suite$class.callExecuteOnSuite$1(Suite.scala:1210)
      at org.scalatest.Suite$$anonfun$runNestedSuites$1.apply(Suite.scala:1257)
      at org.scalatest.Suite$$anonfun$runNestedSuites$1.apply(Suite.scala:1255)
      at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
      at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:186)
      at org.scalatest.Suite$class.runNestedSuites(Suite.scala:1255)
      at org.scalatest.tools.DiscoverySuite.runNestedSuites(DiscoverySuite.scala:30)
      at org.scalatest.Suite$class.run(Suite.scala:1144)
      at org.scalatest.tools.DiscoverySuite.run(DiscoverySuite.scala:30)
      at org.scalatest.tools.SuiteRunner.run(SuiteRunner.scala:45)
      at org.scalatest.tools.Runner$$anonfun$doRunRunRunDaDoRunRun$1.apply(Runner.scala:1340)
      at org.scalatest.tools.Runner$$anonfun$doRunRunRunDaDoRunRun$1.apply(Runner.scala:1334)
      at scala.collection.immutable.List.foreach(List.scala:392)
      at org.scalatest.tools.Runner$.doRunRunRunDaDoRunRun(Runner.scala:1334)
      at org.scalatest.tools.Runner$$anonfun$runOptionallyWithPassFailReporter$2.apply(Runner.scala:1011)
      at org.scalatest.tools.Runner$$anonfun$runOptionallyWithPassFailReporter$2.apply(Runner.scala:1010)
      at org.scalatest.tools.Runner$.withClassLoaderAndDispatchReporter(Runner.scala:1500)
      at org.scalatest.tools.Runner$.runOptionallyWithPassFailReporter(Runner.scala:1010)
      at org.scalatest.tools.Runner$.main(Runner.scala:827)
      at org.scalatest.tools.Runner.main(Runner.scala)