TransformSpecTest should extends InitializedNullHandlingTest (#10392)

diff --git a/server/src/test/java/org/apache/druid/segment/indexing/TransformSpecTest.java b/server/src/test/java/org/apache/druid/segment/indexing/TransformSpecTest.java
index 8102a71..763a924 100644
--- a/server/src/test/java/org/apache/druid/segment/indexing/TransformSpecTest.java
+++ b/server/src/test/java/org/apache/druid/segment/indexing/TransformSpecTest.java
@@ -35,12 +35,13 @@
 import org.apache.druid.segment.TestHelper;
 import org.apache.druid.segment.transform.ExpressionTransform;
 import org.apache.druid.segment.transform.TransformSpec;
+import org.apache.druid.testing.InitializedNullHandlingTest;
 import org.junit.Assert;
 import org.junit.Test;
 
 import java.util.Map;
 
-public class TransformSpecTest
+public class TransformSpecTest extends InitializedNullHandlingTest
 {
   private static final MapInputRowParser PARSER = new MapInputRowParser(
       new TimeAndDimsParseSpec(