diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala
index 095f6a970617b..caf1d206975f0 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoderSuite.scala
@@ -214,7 +214,8 @@ class ExpressionEncoderSuite extends CodegenInterpretedPlanTest with AnalysisTes
     OuterScopes.addOuterScope(MalformedClassObject)
     encodeDecodeTest(
       MalformedClassObject.MalformedNameExample(42),
-      "nested Scala class should work")
+      "nested Scala class should work",
+      useFallback = true)
   }
 
   object OuterLevelWithVeryVeryVeryLongClassName1 {
@@ -284,7 +285,8 @@ class ExpressionEncoderSuite extends CodegenInterpretedPlanTest with AnalysisTes
         .OuterLevelWithVeryVeryVeryLongClassName19
         .OuterLevelWithVeryVeryVeryLongClassName20
         .MalformedNameExample(42),
-      "deeply nested Scala class should work")
+      "deeply nested Scala class should work",
+      useFallback = true)
   }
 
   productTest(PrimitiveData(1, 1, 1, 1, 1, 1, true))
@@ -555,8 +557,9 @@ class ExpressionEncoderSuite extends CodegenInterpretedPlanTest with AnalysisTes
 
   private def encodeDecodeTest[T : ExpressionEncoder](
       input: T,
-      testName: String): Unit = {
-    testAndVerifyNotLeakingReflectionObjects(s"encode/decode for $testName: $input") {
+      testName: String,
+      useFallback: Boolean = false): Unit = {
+    testAndVerifyNotLeakingReflectionObjects(s"encode/decode for $testName: $input", useFallback) {
       val encoder = implicitly[ExpressionEncoder[T]]
 
       // Make sure encoder is serializable.
@@ -650,9 +653,16 @@ class ExpressionEncoderSuite extends CodegenInterpretedPlanTest with AnalysisTes
     r
   }
 
-  private def testAndVerifyNotLeakingReflectionObjects(testName: String)(testFun: => Any): Unit = {
-    test(testName) {
-      verifyNotLeakingReflectionObjects(testFun)
+  private def testAndVerifyNotLeakingReflectionObjects(
+      testName: String, useFallback: Boolean = false)(testFun: => Any): Unit = {
+    if (useFallback) {
+      testFallback(testName) {
+        verifyNotLeakingReflectionObjects(testFun)
+      }
+    } else {
+      test(testName) {
+        verifyNotLeakingReflectionObjects(testFun)
+      }
     }
   }
 }
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala
index e46599dc19a8b..f843784ec52a9 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala
@@ -961,7 +961,7 @@ abstract class AnsiCastSuiteBase extends CastSuiteBase {
   }
 
   test("ANSI mode: cast string to timestamp with parse error") {
-    val activeConf = conf
+    val activeConf = conf.clone()
     new ParVector(ALL_TIMEZONES.toVector).foreach { zid =>
       def checkCastWithParseError(str: String): Unit = {
         checkExceptionInExpression[DateTimeException](
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/PlanTest.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/PlanTest.scala
index 7c70ab98e4183..6bbe99ba7d786 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/PlanTest.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/PlanTest.scala
@@ -51,6 +51,15 @@ trait CodegenInterpretedPlanTest extends PlanTest {
       super.test(testName + " (interpreted path)", testTags: _*)(testFun)(pos)
     }
   }
+
+  protected def testFallback(
+      testName: String,
+      testTags: Tag*)(testFun: => Any)(implicit pos: source.Position): Unit = {
+    val codegenMode = CodegenObjectFactoryMode.FALLBACK.toString
+    withSQLConf(SQLConf.CODEGEN_FACTORY_MODE.key -> codegenMode) {
+      super.test(testName, testTags: _*)(testFun)(pos)
+    }
+  }
 }
 
 /**