diff --git a/core/src/main/scala/org/apache/spark/util/Utils.scala b/core/src/main/scala/org/apache/spark/util/Utils.scala
index 5e68dcd9df7fc..13fcfe4aed023 100644
--- a/core/src/main/scala/org/apache/spark/util/Utils.scala
+++ b/core/src/main/scala/org/apache/spark/util/Utils.scala
@@ -1939,7 +1939,9 @@ private[spark] object Utils extends Logging {
    * Indicates whether Spark is currently running unit tests.
    */
   def isTesting: Boolean = {
-    sys.env.contains("SPARK_TESTING") || sys.props.contains(IS_TESTING.key)
+    // Scala's `sys.env` creates a ton of garbage by constructing Scala immutable maps, so
+    // we directly use the Java APIs instead.
+    System.getenv("SPARK_TESTING") != null || System.getProperty(IS_TESTING.key) != null
   }
 
   /**