Create TortoiseHareAlgoTest.java

Add JUnit tests for TortoiseHareAlgo

- Verified append() and toString() output
- Tested getMiddle() for odd, even, and empty lists
- Ensured correct behavior and null handling

Author: TejasSingh022

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

@@ -0,0 +1,44 @@
+package com.thealgorithms.datastructures.lists;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class TortoiseHareAlgoTest {
+
+    @Test
+    void testAppendAndToString() {
+        TortoiseHareAlgo<Integer> list = new TortoiseHareAlgo<>();
+        list.append(10);
+        list.append(20);
+        list.append(30);
+        assertEquals("[10, 20, 30]", list.toString());
+    }
+
+    @Test
+    void testGetMiddleOdd() {
+        TortoiseHareAlgo<Integer> list = new TortoiseHareAlgo<>();
+        list.append(1);
+        list.append(2);
+        list.append(3);
+        list.append(4);
+        list.append(5);
+        assertEquals(3, list.getMiddle());
+    }
+
+    @Test
+    void testGetMiddleEven() {
+        TortoiseHareAlgo<Integer> list = new TortoiseHareAlgo<>();
+        list.append(1);
+        list.append(2);
+        list.append(3);
+        list.append(4);
+        assertEquals(3, list.getMiddle()); // returns second middle
+    }
+
+    @Test
+    void testEmptyList() {
+        TortoiseHareAlgo<Integer> list = new TortoiseHareAlgo<>();
+        assertNull(list.getMiddle());
+        assertEquals("[]", list.toString());
+    }
+}