Small assertion cleanup.

sql/core/src/test/scala/org/apache/spark/sql/execution/PlannerSuite.scala

@@ -209,6 +209,19 @@ class PlannerSuite extends SparkFunSuite with SQLTestUtils {
 
   // --- Unit tests of EnsureRequirements ---------------------------------------------------------
 
+  private def assertDistributionRequirementsAreSatisfied(outputPlan: SparkPlan): Unit = {
+    if (outputPlan.requiresChildrenToProduceSameNumberOfPartitions) {
+      if (outputPlan.children.map(_.outputPartitioning.numPartitions).toSet.size != 1) {
+        fail(s"Children did not produce the same number of partitions:\n$outputPlan")
+      }
+    }
+    outputPlan.children.zip(outputPlan.requiredChildDistribution).foreach {
+      case (child, requiredDist) =>
+        assert(child.outputPartitioning.satisfies(requiredDist),
+          s"$child output partitioning does not satisfy $requiredDist:\n$outputPlan")
+    }
+  }
+
   test("EnsureRequirements ensures that children produce same number of partitions when required") {
     val clustering = Literal(1) :: Nil
     val distribution = ClusteredDistribution(clustering)
@@ -222,7 +235,7 @@ class PlannerSuite extends SparkFunSuite with SQLTestUtils {
       requiredChildOrdering = Seq(Seq.empty, Seq.empty)
     )
     val outputPlan = EnsureRequirements(sqlContext).apply(inputPlan)
-    assert (outputPlan.children.map(_.outputPartitioning.numPartitions).toSet.size === 1)
+    assertDistributionRequirementsAreSatisfied(outputPlan)
   }
 
   test("EnsureRequirements should not repartition if only ordering requirement is unsatisfied") {
@@ -238,6 +251,7 @@ class PlannerSuite extends SparkFunSuite with SQLTestUtils {
       requiredChildOrdering = Seq(outputOrdering, outputOrdering)
     )
     val outputPlan = EnsureRequirements(sqlContext).apply(inputPlan)
+    assertDistributionRequirementsAreSatisfied(outputPlan)
     if (outputPlan.collect { case Exchange(_, _) => true }.nonEmpty) {
       fail(s"No Exchanges should have been added:\n$outputPlan")
     }