fix: correct import order for clang-format compliance

Author: gowtham1412-p

src/test/java/com/thealgorithms/datastructures/stacks/StackUsingLinkedListTest.java

@@ -1,69 +1,103 @@
 package com.thealgorithms.datastructures.stacks;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import org.junit.jupiter.api.Test;
-import static org.junit.jupiter.api.Assertions.*;
 
 class StackUsingLinkedListTest {
-    
+
     @Test
     void testPushAndPop() {
         StackUsingLinkedList stack = new StackUsingLinkedList();
         stack.push(10);
         stack.push(20);
         stack.push(30);
-        
+
         assertEquals(30, stack.pop());
         assertEquals(20, stack.pop());
         assertEquals(10, stack.pop());
     }
-    
+
     @Test
     void testPeek() {
         StackUsingLinkedList stack = new StackUsingLinkedList();
         stack.push(100);
         stack.push(200);
-        
+
         assertEquals(200, stack.peek());
         assertEquals(200, stack.peek());
+        assertEquals(2, stack.size());
     }
-    
+
     @Test
     void testIsEmpty() {
         StackUsingLinkedList stack = new StackUsingLinkedList();
         assertTrue(stack.isEmpty());
-        
+
         stack.push(5);
         assertFalse(stack.isEmpty());
-        
+
         stack.pop();
         assertTrue(stack.isEmpty());
     }
-    
+
     @Test
     void testSize() {
         StackUsingLinkedList stack = new StackUsingLinkedList();
         assertEquals(0, stack.size());
-        
+
         stack.push(1);
         assertEquals(1, stack.size());
-        
+
         stack.push(2);
         stack.push(3);
         assertEquals(3, stack.size());
-        
+
         stack.pop();
         assertEquals(2, stack.size());
     }
-    
+
     @Test
     void testPopEmptyStack() {
         StackUsingLinkedList stack = new StackUsingLinkedList();
-        assertThrows(RuntimeException.class, () -> stack.pop());
+        assertThrows(RuntimeException.class, stack::pop);
     }
-    
+
     @Test
     void testPeekEmptyStack() {
         StackUsingLinkedList stack = new StackUsingLinkedList();
-        assertThrows(RuntimeException.class, () -> stack.peek());
+        assertThrows(RuntimeException.class, stack::peek);
+    }
+
+    @Test
+    void testMultipleOperations() {
+        StackUsingLinkedList stack = new StackUsingLinkedList();
+
+        assertTrue(stack.isEmpty());
+
+        stack.push(1);
+        stack.push(2);
+        assertEquals(2, stack.pop());
+
+        stack.push(3);
+        stack.push(4);
+        assertEquals(4, stack.peek());
+        assertEquals(3, stack.size());
+
+        assertFalse(stack.isEmpty());
+    }
+
+    @Test
+    void testSingleElement() {
+        StackUsingLinkedList stack = new StackUsingLinkedList();
+        stack.push(42);
+
+        assertEquals(42, stack.peek());
+        assertEquals(1, stack.size());
+        assertEquals(42, stack.pop());
+        assertTrue(stack.isEmpty());
     }
 }