Create CircularDoublyLinkedListTest.java

added tests for CircularDoublyLinkedListTest

Author: richk21

src/test/java/com/thealgorithms/datastructures/lists/CircularDoublyLinkedListTest.java

@@ -0,0 +1,83 @@
+package com.thealgorithms.datastructures.lists;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class CircularDoublyLinkedListTest {
+
+    private CircularDoublyLinkedList<Integer> list;
+
+    @BeforeEach
+    public void setUp() {
+        list = new CircularDoublyLinkedList<>();
+    }
+
+    @Test
+    public void testInitialSize() {
+        assertEquals(0, list.getSize(), "Initial size should be 0.");
+    }
+
+    @Test
+    public void testAppendAndSize() {
+        list.append(10);
+        list.append(20);
+        list.append(30);
+
+        assertEquals(3, list.getSize(), "Size after appends should be 3.");
+        assertEquals("[ 10, 20, 30 ]", list.toString(), "List content should match appended values.");
+    }
+
+    @Test
+    public void testRemove() {
+        list.append(10);
+        list.append(20);
+        list.append(30);
+
+        int removed = list.remove(1);
+        assertEquals(20, removed, "Removed element at index 1 should be 20.");
+
+        assertEquals("[ 10, 30 ]", list.toString(), "List content should reflect removal.");
+        assertEquals(2, list.getSize(), "Size after removal should be 2.");
+
+        removed = list.remove(0);
+        assertEquals(10, removed, "Removed element at index 0 should be 10.");
+        assertEquals("[ 30 ]", list.toString(), "List content should reflect second removal.");
+        assertEquals(1, list.getSize(), "Size after second removal should be 1.");
+    }
+
+    @Test
+    public void testRemoveInvalidIndex() {
+        list.append(10);
+        list.append(20);
+
+        assertThrows(IndexOutOfBoundsException.class, () -> list.remove(2),
+                "Removing at invalid index 2 should throw exception.");
+        assertThrows(IndexOutOfBoundsException.class, () -> list.remove(-1),
+                "Removing at negative index should throw exception.");
+    }
+
+    @Test
+    public void testToStringEmpty() {
+        assertEquals("[]", list.toString(), "Empty list should display as [].");
+    }
+
+    @Test
+    public void testSingleElement() {
+        list.append(10);
+
+        assertEquals(1, list.getSize(), "Size after adding single element should be 1.");
+        assertEquals("[ 10 ]", list.toString(), "Single element list string should be formatted correctly.");
+        int removed = list.remove(0);
+        assertEquals(10, removed, "Removed element should be the one appended.");
+        assertEquals("[]", list.toString(), "List should be empty after removing last element.");
+        assertEquals(0, list.getSize(), "Size after removing last element should be 0.");
+    }
+
+    @Test
+    public void testNullAppend() {
+        assertThrows(NullPointerException.class, () -> list.append(null),
+                "Appending null should throw NullPointerException.");
+    }
+}