diff --git a/test/com/deepak/data/structures/Queue/ArrayBasedQueueTest.java b/test/com/deepak/data/structures/Queue/ArrayBasedQueueTest.java
index a2764b2..f5c7e7d 100644
--- a/test/com/deepak/data/structures/Queue/ArrayBasedQueueTest.java
+++ b/test/com/deepak/data/structures/Queue/ArrayBasedQueueTest.java
@@ -2,6 +2,7 @@
  * Data-Structures-In-Java
  * ArrayBasedQueueTest.java
  */
+// Queue uses FIFO(First In First Out) principle.
 package com.deepak.data.structures.Queue;
 
 import org.junit.Assert;
diff --git a/test/com/deepak/data/structures/Stack/ArrayBasedStackTest.java b/test/com/deepak/data/structures/Stack/ArrayBasedStackTest.java
index 91f1b16..470ab62 100644
--- a/test/com/deepak/data/structures/Stack/ArrayBasedStackTest.java
+++ b/test/com/deepak/data/structures/Stack/ArrayBasedStackTest.java
@@ -2,6 +2,7 @@
  * Data-Structures-In-Java
  * ArrayBasedStackTest.java
  */
+//Stack uses LIFO(Last In First Out) principle.
 package com.deepak.data.structures.Stack;
 
 import org.junit.Assert;