testing: improving DequeTest (#6410)

alxkm · DenizAltunkapan · web-flow · commit 75298bb3f4a4 · 2025-07-21T15:58:22.000Z
* testing: improving DequeTest

* testing: redundant case

* testing: fix to many static imports

* testing: add more test cases

---------

Co-authored-by: Deniz Altunkapan &lt;93663085+DenizAltunkapan@users.noreply.github.com&gt;
diff --git a/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java b/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
@@ -87,4 +87,38 @@ void testToString() {
         deque.addFirst(5);
         assertEquals("Head -> 5 <-> 10 <-> 20 <- Tail", deque.toString());
     }
+
+    @Test
+    void testAlternatingAddRemove() {
+        Deque<Integer> deque = new Deque<>();
+        deque.addFirst(1);
+        deque.addLast(2);
+        deque.addFirst(0);
+        assertEquals(0, deque.pollFirst());
+        assertEquals(2, deque.pollLast());
+        assertEquals(1, deque.pollFirst());
+        org.junit.jupiter.api.Assertions.assertTrue(deque.isEmpty());
+    }
+
+    @Test
+    void testSizeAfterOperations() {
+        Deque<Integer> deque = new Deque<>();
+        assertEquals(0, deque.size());
+        deque.addFirst(1);
+        deque.addLast(2);
+        deque.addFirst(3);
+        assertEquals(3, deque.size());
+        deque.pollFirst();
+        deque.pollLast();
+        assertEquals(1, deque.size());
+    }
+
+    @Test
+    void testNullValues() {
+        Deque<String> deque = new Deque<>();
+        deque.addFirst(null);
+        assertNull(deque.peekFirst());
+        assertNull(deque.pollFirst());
+        org.junit.jupiter.api.Assertions.assertTrue(deque.isEmpty());
+    }
 }
