[MINOR] Optimize code style for test of backend-velox

backends-velox/src/test/scala/org/apache/gluten/execution/DynamicOffHeapSizingSuite.scala

@@ -53,7 +53,6 @@ class DynamicOffHeapSizingSuite extends VeloxWholeStageTransformerSuite {
       """.stripMargin
       var totalMemory = Runtime.getRuntime().totalMemory()
       var freeMemory = Runtime.getRuntime().freeMemory()
-      val maxMemory = Runtime.getRuntime().maxMemory()
       // Ensure that the JVM memory is not too small to trigger dynamic off-heap sizing.
       while (!DynamicOffHeapSizingMemoryTarget.canShrinkJVMMemory(totalMemory, freeMemory)) {
         withSQLConf(("spark.gluten.enabled", "false")) {

backends-velox/src/test/scala/org/apache/gluten/execution/FallbackSuite.scala

@@ -123,7 +123,7 @@ class FallbackSuite extends VeloxWholeStageTransformerSuite with AdaptiveSparkPl
             case _: BroadcastHashJoinExecTransformerBase => true
             case _ => false
           }
-          assert(!columnarBhj.isDefined)
+          assert(columnarBhj.isEmpty)
 
           val vanillaBhj = find(plan) {
             case _: BroadcastHashJoinExec => true

backends-velox/src/test/scala/org/apache/gluten/execution/GlutenSQLCollectTailExecSuite.scala

@@ -98,7 +98,6 @@ class GlutenSQLCollectTailExecSuite extends WholeStageTransformerSuite {
 
   test("ColumnarCollectTailExec - with filter") {
     val df = spark.range(0, 10000, 1).toDF("id").filter("id % 2 == 0").orderBy("id")
-    val evenCount = 5000
     val expected = (9990L to 9998L by 2).map(Row(_)).takeRight(5)
     verifyTailExec(df, expected, tailCount = 5)
   }

backends-velox/src/test/scala/org/apache/gluten/execution/MiscOperatorSuite.scala

@@ -332,7 +332,7 @@ class MiscOperatorSuite extends VeloxWholeStageTransformerSuite with AdaptiveSpa
   }
 
   test("group sets") {
-    val result = runQueryAndCompare(
+    runQueryAndCompare(
       "select l_orderkey, l_partkey, sum(l_suppkey) from lineitem " +
         "where l_orderkey < 3 group by ROLLUP(l_orderkey, l_partkey) " +
         "order by l_orderkey, l_partkey ") { _ => }
@@ -583,13 +583,13 @@ class MiscOperatorSuite extends VeloxWholeStageTransformerSuite with AdaptiveSpa
   }
 
   test("union two tables") {
-    val df = runQueryAndCompare("""
-                                  |select count(orderkey) from (
-                                  | select l_orderkey as orderkey from lineitem
-                                  | union
-                                  | select o_orderkey as orderkey from orders
-                                  |);
-                                  |""".stripMargin) {
+    runQueryAndCompare("""
+                         |select count(orderkey) from (
+                         | select l_orderkey as orderkey from lineitem
+                         | union
+                         | select o_orderkey as orderkey from orders
+                         |);
+                         |""".stripMargin) {
       df =>
         {
           getExecutedPlan(df).exists(plan => plan.find(_.isInstanceOf[ColumnarUnionExec]).isDefined)

backends-velox/src/test/scala/org/apache/gluten/execution/VeloxAggregateFunctionsSuite.scala

@@ -53,10 +53,9 @@ abstract class VeloxAggregateFunctionsSuite extends VeloxWholeStageTransformerSu
   }
 
   test("count") {
-    val df =
-      runQueryAndCompare("select count(*) from lineitem where l_partkey in (1552, 674, 1062)") {
-        checkGlutenOperatorMatch[HashAggregateExecTransformer]
-      }
+    runQueryAndCompare("select count(*) from lineitem where l_partkey in (1552, 674, 1062)") {
+      checkGlutenOperatorMatch[HashAggregateExecTransformer]
+    }
     runQueryAndCompare("select count(l_quantity), count(distinct l_partkey) from lineitem") {
       df =>
         {
@@ -70,7 +69,7 @@ abstract class VeloxAggregateFunctionsSuite extends VeloxWholeStageTransformerSu
   }
 
   test("avg") {
-    val df = runQueryAndCompare("select avg(l_partkey) from lineitem where l_partkey < 1000") {
+    runQueryAndCompare("select avg(l_partkey) from lineitem where l_partkey < 1000") {
       checkGlutenOperatorMatch[HashAggregateExecTransformer]
     }
     runQueryAndCompare("select avg(l_quantity), count(distinct l_partkey) from lineitem") {
@@ -215,7 +214,7 @@ abstract class VeloxAggregateFunctionsSuite extends VeloxWholeStageTransformerSu
   }
 
   test("group sets") {
-    val result = runQueryAndCompare(
+    runQueryAndCompare(
       "select l_orderkey, l_partkey, sum(l_suppkey) from lineitem " +
         "where l_orderkey < 3 group by ROLLUP(l_orderkey, l_partkey) " +
         "order by l_orderkey, l_partkey ") { _ => }

backends-velox/src/test/scala/org/apache/gluten/execution/VeloxHashJoinSuite.scala

@@ -159,8 +159,8 @@ class VeloxHashJoinSuite extends VeloxWholeStageTransformerSuite {
     Seq("true", "false").foreach(
       enabledOffheapBroadcast =>
         withSQLConf(
-          (GlutenConfig.GLUTEN_COLUMNAR_TO_ROW_MEM_THRESHOLD.key -> "16"),
-          (VeloxConfig.VELOX_BROADCAST_BUILD_RELATION_USE_OFFHEAP.key -> enabledOffheapBroadcast)) {
+          GlutenConfig.GLUTEN_COLUMNAR_TO_ROW_MEM_THRESHOLD.key -> "16",
+          VeloxConfig.VELOX_BROADCAST_BUILD_RELATION_USE_OFFHEAP.key -> enabledOffheapBroadcast) {
           withTable("t1", "t2") {
             spark.sql("""
                         |CREATE TABLE t1 USING PARQUET

backends-velox/src/test/scala/org/apache/gluten/execution/VeloxScanSuite.scala

@@ -94,9 +94,9 @@ class VeloxScanSuite extends VeloxWholeStageTransformerSuite {
               val plan = df.queryExecution.executedPlan
               val fileScan = collect(plan) { case s: FileSourceScanExecTransformer => s }
               assert(fileScan.size == 1)
-              val rootPaths = fileScan(0).getRootPathsInternal
+              val rootPaths = fileScan.head.getRootPathsInternal
               assert(rootPaths.length == 1)
-              assert(rootPaths(0).startsWith("file:/"))
+              assert(rootPaths.head.startsWith("file:/"))
               assert(
                 VeloxFileSystemValidationJniWrapper.allSupportedByRegisteredFileSystems(
                   rootPaths.toArray))
@@ -107,7 +107,7 @@ class VeloxScanSuite extends VeloxWholeStageTransformerSuite {
       VeloxBackendSettings.distinctRootPaths(
         Seq("file:/test_path/", "test://test/s", "test://test1/s"))
     assert(filteredRootPath.length == 1)
-    assert(filteredRootPath(0).startsWith("test://"))
+    assert(filteredRootPath.head.startsWith("test://"))
     assert(
       VeloxFileSystemValidationJniWrapper.allSupportedByRegisteredFileSystems(
         Array("file:/test_path/")))

backends-velox/src/test/scala/org/apache/gluten/extension/columnar/enumerated/planner/VeloxRasSuite.scala

@@ -89,7 +89,7 @@ class VeloxRasSuite extends SharedSparkSession {
     object ConvertRowUnaryToColumnar extends RasRule[SparkPlan] {
       override def shift(node: SparkPlan): Iterable[SparkPlan] = node match {
         case RowUnary(child) => List(ColumnarUnary(child))
-        case other => List.empty
+        case _ => List.empty
       }
 
       override def shape(): Shape[SparkPlan] = Shapes.fixedHeight(1)