From 158ee510c85f0e90f2d4a435698649b261a9c372 Mon Sep 17 00:00:00 2001
From: alxkm <alexanderklmn@gmail.com>
Date: Fri, 18 Jul 2025 19:51:53 +0200
Subject: [PATCH 1/4] testing: improving DequeTest

---
 .../datastructures/queues/DequeTest.java      | 26 ++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java b/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
index 1244a2e260d2..4b3551ed86ac 100644
--- a/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
+++ b/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
@@ -3,6 +3,8 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.NoSuchElementException;
 import org.junit.jupiter.api.Test;
@@ -50,7 +52,7 @@ void testPollLast() {
     @Test
     void testIsEmpty() {
         Deque<Integer> deque = new Deque<>();
-        org.junit.jupiter.api.Assertions.assertTrue(deque.isEmpty());
+        assertTrue(deque.isEmpty());
         deque.addFirst(10);
         assertFalse(deque.isEmpty());
     }
@@ -70,13 +72,13 @@ void testPeekLastEmpty() {
     @Test
     void testPollFirstEmpty() {
         Deque<Integer> deque = new Deque<>();
-        org.junit.jupiter.api.Assertions.assertThrows(NoSuchElementException.class, deque::pollFirst);
+        assertThrows(NoSuchElementException.class, deque::pollFirst);
     }
 
     @Test
     void testPollLastEmpty() {
         Deque<Integer> deque = new Deque<>();
-        org.junit.jupiter.api.Assertions.assertThrows(NoSuchElementException.class, deque::pollLast);
+        assertThrows(NoSuchElementException.class, deque::pollLast);
     }
 
     @Test
@@ -87,4 +89,22 @@ 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());
+        assertTrue(deque.isEmpty());
+    }
+
+    @Test
+    void testAddNull() {
+        Deque<Integer> deque = new Deque<>();
+        assertThrows(NullPointerException.class, () -> deque.addFirst(null));
+    }
 }

From f62bbc332aa5a03a7bf81f6d77d432ec0324569c Mon Sep 17 00:00:00 2001
From: alxkm <alexanderklmn@gmail.com>
Date: Fri, 18 Jul 2025 19:58:34 +0200
Subject: [PATCH 2/4] testing: redundant case

---
 .../com/thealgorithms/datastructures/queues/DequeTest.java  | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java b/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
index 4b3551ed86ac..ec77b0c25507 100644
--- a/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
+++ b/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
@@ -101,10 +101,4 @@ void testAlternatingAddRemove() {
         assertEquals(1, deque.pollFirst());
         assertTrue(deque.isEmpty());
     }
-
-    @Test
-    void testAddNull() {
-        Deque<Integer> deque = new Deque<>();
-        assertThrows(NullPointerException.class, () -> deque.addFirst(null));
-    }
 }

From d7f156187300fa31a67514c06cf0c883f4429074 Mon Sep 17 00:00:00 2001
From: alxkm <alexanderklmn@gmail.com>
Date: Fri, 18 Jul 2025 20:02:24 +0200
Subject: [PATCH 3/4] testing: fix to many static imports

---
 .../com/thealgorithms/datastructures/queues/DequeTest.java  | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java b/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
index ec77b0c25507..26fef27ea4bc 100644
--- a/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
+++ b/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
@@ -1,10 +1,6 @@
 package com.thealgorithms.datastructures.queues;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertNull;
-import static org.junit.jupiter.api.Assertions.assertThrows;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.*;
 
 import java.util.NoSuchElementException;
 import org.junit.jupiter.api.Test;

From 37de6e80a66940c536d6e7dc5d6b3a7529427fc8 Mon Sep 17 00:00:00 2001
From: alxkm <alexanderklmn@gmail.com>
Date: Fri, 18 Jul 2025 20:10:11 +0200
Subject: [PATCH 4/4] testing: add more test cases

---
 .../datastructures/queues/DequeTest.java      | 34 ++++++++++++++++---
 1 file changed, 29 insertions(+), 5 deletions(-)

diff --git a/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java b/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
index 26fef27ea4bc..34b1ea2e0277 100644
--- a/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
+++ b/src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
@@ -1,6 +1,8 @@
 package com.thealgorithms.datastructures.queues;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
 
 import java.util.NoSuchElementException;
 import org.junit.jupiter.api.Test;
@@ -48,7 +50,7 @@ void testPollLast() {
     @Test
     void testIsEmpty() {
         Deque<Integer> deque = new Deque<>();
-        assertTrue(deque.isEmpty());
+        org.junit.jupiter.api.Assertions.assertTrue(deque.isEmpty());
         deque.addFirst(10);
         assertFalse(deque.isEmpty());
     }
@@ -68,13 +70,13 @@ void testPeekLastEmpty() {
     @Test
     void testPollFirstEmpty() {
         Deque<Integer> deque = new Deque<>();
-        assertThrows(NoSuchElementException.class, deque::pollFirst);
+        org.junit.jupiter.api.Assertions.assertThrows(NoSuchElementException.class, deque::pollFirst);
     }
 
     @Test
     void testPollLastEmpty() {
         Deque<Integer> deque = new Deque<>();
-        assertThrows(NoSuchElementException.class, deque::pollLast);
+        org.junit.jupiter.api.Assertions.assertThrows(NoSuchElementException.class, deque::pollLast);
     }
 
     @Test
@@ -95,6 +97,28 @@ void testAlternatingAddRemove() {
         assertEquals(0, deque.pollFirst());
         assertEquals(2, deque.pollLast());
         assertEquals(1, deque.pollFirst());
-        assertTrue(deque.isEmpty());
+        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());
     }
 }

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