ReverseStackUsingRecursionTest.java

packagecom.thealgorithms.others;

importstaticorg.junit.jupiter.api.Assertions.assertEquals;
importstaticorg.junit.jupiter.api.Assertions.assertThrows;
importstaticorg.junit.jupiter.api.Assertions.assertTrue;

importjava.util.Stack;
importorg.junit.jupiter.api.Test;

publicclassReverseStackUsingRecursionTest {

@Test
voidtestReverseWithMultipleElements() {
Stack<Integer> stack = newStack<>();
for (inti = 0; i < 5; i++) {
stack.push(i);
 }

ReverseStackUsingRecursion.reverse(stack);

for (inti = 0; i < 5; i++) {
assertEquals(i, stack.pop());
 }
assertTrue(stack.isEmpty());
 }

@Test
voidtestReverseWithSingleElement() {
Stack<Integer> stack = newStack<>();
stack.push(1);

ReverseStackUsingRecursion.reverse(stack);

assertEquals(1, stack.pop());
assertTrue(stack.isEmpty());
 }

@Test
voidtestReverseWithEmptyStack() {
Stack<Integer> stack = newStack<>();

ReverseStackUsingRecursion.reverse(stack);

assertTrue(stack.isEmpty());
 }

@Test
voidtestReverseWithNullStack() {
Stack<Integer> stack = null;

Exceptionexception = assertThrows(IllegalArgumentException.class, () -> ReverseStackUsingRecursion.reverse(stack));

StringexpectedMessage = "Stack cannot be null";
StringactualMessage = exception.getMessage();

assertTrue(actualMessage.contains(expectedMessage));
 }
}