refactor: Deque (#5353)

src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java

@@ -0,0 +1,90 @@
+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 java.util.NoSuchElementException;
+import org.junit.jupiter.api.Test;
+
+class DequeTest {
+
+    @Test
+    void testAddFirst() {
+        Deque<Integer> deque = new Deque<>();
+        deque.addFirst(10);
+        assertEquals(10, deque.peekFirst());
+        assertEquals(10, deque.peekLast());
+        assertEquals(1, deque.size());
+    }
+
+    @Test
+    void testAddLast() {
+        Deque<Integer> deque = new Deque<>();
+        deque.addLast(20);
+        assertEquals(20, deque.peekFirst());
+        assertEquals(20, deque.peekLast());
+        assertEquals(1, deque.size());
+    }
+
+    @Test
+    void testPollFirst() {
+        Deque<Integer> deque = new Deque<>();
+        deque.addFirst(10);
+        deque.addLast(20);
+        assertEquals(10, deque.pollFirst());
+        assertEquals(20, deque.peekFirst());
+        assertEquals(1, deque.size());
+    }
+
+    @Test
+    void testPollLast() {
+        Deque<Integer> deque = new Deque<>();
+        deque.addFirst(10);
+        deque.addLast(20);
+        assertEquals(20, deque.pollLast());
+        assertEquals(10, deque.peekLast());
+        assertEquals(1, deque.size());
+    }
+
+    @Test
+    void testIsEmpty() {
+        Deque<Integer> deque = new Deque<>();
+        org.junit.jupiter.api.Assertions.assertTrue(deque.isEmpty());
+        deque.addFirst(10);
+        assertFalse(deque.isEmpty());
+    }
+
+    @Test
+    void testPeekFirstEmpty() {
+        Deque<Integer> deque = new Deque<>();
+        assertNull(deque.peekFirst());
+    }
+
+    @Test
+    void testPeekLastEmpty() {
+        Deque<Integer> deque = new Deque<>();
+        assertNull(deque.peekLast());
+    }
+
+    @Test
+    void testPollFirstEmpty() {
+        Deque<Integer> deque = new Deque<>();
+        org.junit.jupiter.api.Assertions.assertThrows(NoSuchElementException.class, deque::pollFirst);
+    }
+
+    @Test
+    void testPollLastEmpty() {
+        Deque<Integer> deque = new Deque<>();
+        org.junit.jupiter.api.Assertions.assertThrows(NoSuchElementException.class, deque::pollLast);
+    }
+
+    @Test
+    void testToString() {
+        Deque<Integer> deque = new Deque<>();
+        deque.addFirst(10);
+        deque.addLast(20);
+        deque.addFirst(5);
+        assertEquals("Head -> 5 <-> 10 <-> 20 <- Tail", deque.toString());
+    }
+}