feat: added test cases for deque

Author: yeoshuheng

test/dataStructures/queue/dequeTest.java

@@ -1,2 +1,61 @@
-package test.dataStructures.queue;public class dequeTest {
+package test.dataStructures.queue;
+
+import org.junit.Assert;
+import org.junit.Test;
+import src.dataStructures.queue.Deque;
+
+import java.util.Optional;
+
+public class dequeTest {
+
+    @Test
+    public void testEmpty() {
+        Deque<Integer> d = new Deque<>();
+        Assert.assertEquals(true, d.isEmpty());
+        Assert.assertEquals(0, d.getSize());
+        Assert.assertEquals(d.peekFirst(), null);
+        Assert.assertEquals(d.peekLast(), null);
+    }
+
+    @Test
+    public void testInsertion() {
+        Deque<Integer> d = new Deque<>();
+        Assert.assertEquals("[]", d.toString());
+        d.addElement(2);
+        d.addElement(3);
+        d.addFirst(1);
+        Assert.assertEquals("[ 1  2  3 ]", d.toString());
+        Assert.assertEquals(3, d.getSize());
+    }
+
+    @Test
+    public void testPeek() {
+        Deque<Integer> d = new Deque<>();
+        Assert.assertEquals(null, d.peekFirst());
+        Assert.assertEquals(null, d.peekLast());
+        d.addElement(1);
+        d.addElement(2);
+        d.addElement(3);
+        d.peekLast();
+        Assert.assertEquals(3, d.getSize());
+        Assert.assertEquals(Optional.of(1).get(), d.peekFirst());
+        Assert.assertEquals(Optional.of(3).get(), d.peekLast());
+    }
+
+    @Test
+    public void testPoll() {
+        Deque<Integer> d = new Deque<>();
+        Assert.assertEquals(null, d.pollFirst());
+        Assert.assertEquals(null, d.pollLast());
+        d.addElement(1);
+        d.addElement(2);
+        d.addElement(3);
+        Assert.assertEquals(Optional.of(1).get(), d.pollFirst());
+        Assert.assertEquals(Optional.of(3).get(), d.pollLast());
+        Assert.assertEquals(1, d.getSize());
+        Assert.assertEquals("[ 2 ]", d.toString());
+        Assert.assertEquals(Optional.of(2).get(), d.pollLast());
+        Assert.assertEquals(0, d.getSize());
+    }
+
 }