Make test more explicit

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/RewriteSubquerySuite.scala

@@ -20,11 +20,11 @@ package org.apache.spark.sql.catalyst.optimizer
 import org.apache.spark.sql.catalyst.QueryPlanningTracker
 import org.apache.spark.sql.catalyst.dsl.expressions._
 import org.apache.spark.sql.catalyst.dsl.plans._
-import org.apache.spark.sql.catalyst.expressions.{IsNull, ListQuery, Not}
-import org.apache.spark.sql.catalyst.expressions.aggregate.AggregateExpression
+import org.apache.spark.sql.catalyst.expressions.{Cast, IsNull, ListQuery, Not}
 import org.apache.spark.sql.catalyst.plans.{ExistenceJoin, LeftSemi, PlanTest}
-import org.apache.spark.sql.catalyst.plans.logical.{Join, LocalRelation, LogicalPlan}
+import org.apache.spark.sql.catalyst.plans.logical.{LocalRelation, LogicalPlan}
 import org.apache.spark.sql.catalyst.rules.RuleExecutor
+import org.apache.spark.sql.types.LongType
 
 
 class RewriteSubquerySuite extends PlanTest {
@@ -84,10 +84,16 @@ class RewriteSubquerySuite extends PlanTest {
   test("SPARK-50091: Don't put aggregate expression in join condition") {
     val relation1 = LocalRelation($"c1".int, $"c2".int, $"c3".int)
     val relation2 = LocalRelation($"col1".int, $"col2".int, $"col3".int)
-    val query = relation2.select(sum($"col2").in(ListQuery(relation1.select($"c3"))))
-
-    val optimized = Optimize.execute(query.analyze)
-    val join = optimized.find(_.isInstanceOf[Join]).get.asInstanceOf[Join]
-    assert(!join.condition.get.exists(_.isInstanceOf[AggregateExpression]))
+    val plan = relation2.groupBy()(sum($"col2").in(ListQuery(relation1.select($"c3"))))
+    val optimized = Optimize.execute(plan.analyze)
+    val aggregate = relation2
+      .select($"col2")
+      .groupBy()(sum($"col2").as("_aggregateexpression"))
+    val correctAnswer = aggregate
+      .join(relation1.select(Cast($"c3", LongType).as("c3")),
+        ExistenceJoin($"exists".boolean.withNullability(false)),
+        Some($"_aggregateexpression" === $"c3"))
+      .select($"exists".as("(sum(col2) IN (listquery()))")).analyze
+    comparePlans(optimized, correctAnswer)
   }
 }