From db3a052c0e208e5b6166c5ac39fa9c7471dfb252 Mon Sep 17 00:00:00 2001
From: alxkm <alexanderklmn@gmail.com>
Date: Mon, 14 Jul 2025 19:56:25 +0200
Subject: [PATCH 1/2] testing: added unit tests for the MinStackUsingTwoStacks

---
 .../stacks/MinStackUsingTwoStacksTest.java    | 88 +++++++++++++++++--
 1 file changed, 81 insertions(+), 7 deletions(-)

diff --git a/src/test/java/com/thealgorithms/stacks/MinStackUsingTwoStacksTest.java b/src/test/java/com/thealgorithms/stacks/MinStackUsingTwoStacksTest.java
index e5deb17e9a8f..ec993fd2f1e0 100644
--- a/src/test/java/com/thealgorithms/stacks/MinStackUsingTwoStacksTest.java
+++ b/src/test/java/com/thealgorithms/stacks/MinStackUsingTwoStacksTest.java
@@ -1,38 +1,112 @@
 package com.thealgorithms.stacks;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;
+import java.util.EmptyStackException;
 
 public class MinStackUsingTwoStacksTest {
 
     @Test
-    public void testMinStackOperations() {
+    public void testBasicOperations() {
         MinStackUsingTwoStacks minStack = new MinStackUsingTwoStacks();
         minStack.push(3);
         minStack.push(5);
-        assertEquals(3, minStack.getMin());
+        assertEquals(3, minStack.getMin(), "Min should be 3");
 
         minStack.push(2);
         minStack.push(1);
-        assertEquals(1, minStack.getMin());
+        assertEquals(1, minStack.getMin(), "Min should be 1");
 
         minStack.pop();
-        assertEquals(2, minStack.getMin());
+        assertEquals(2, minStack.getMin(), "Min should be 2 after popping 1");
+
+        assertEquals(2, minStack.top(), "Top should be 2");
+    }
+
+    @Test
+    public void testPushDuplicateMins() {
+        MinStackUsingTwoStacks minStack = new MinStackUsingTwoStacks();
+        minStack.push(2);
+        minStack.push(2);
+        minStack.push(1);
+        minStack.push(1);
+        assertEquals(1, minStack.getMin(), "Min should be 1");
+
+        minStack.pop();
+        assertEquals(1, minStack.getMin(), "Min should still be 1 after popping one 1");
+
+        minStack.pop();
+        assertEquals(2, minStack.getMin(), "Min should be 2 after popping both 1s");
+
+        minStack.pop();
+        assertEquals(2, minStack.getMin(), "Min should still be 2 after popping one 2");
+
+        minStack.pop();
+        // Now stack is empty, expect exception on getMin
+        assertThrows(EmptyStackException.class, minStack::getMin);
     }
 
     @Test
-    public void testMinStackOperations2() {
+    public void testPopOnEmptyStack() {
         MinStackUsingTwoStacks minStack = new MinStackUsingTwoStacks();
+        assertThrows(EmptyStackException.class, minStack::pop);
+    }
+
+    @Test
+    public void testTopOnEmptyStack() {
+        MinStackUsingTwoStacks minStack = new MinStackUsingTwoStacks();
+        assertThrows(EmptyStackException.class, minStack::top);
+    }
+
+    @Test
+    public void testGetMinOnEmptyStack() {
+        MinStackUsingTwoStacks minStack = new MinStackUsingTwoStacks();
+        assertThrows(EmptyStackException.class, minStack::getMin);
+    }
+
+    @Test
+    public void testSingleElementStack() {
+        MinStackUsingTwoStacks minStack = new MinStackUsingTwoStacks();
+        minStack.push(10);
+        assertEquals(10, minStack.getMin());
+        assertEquals(10, minStack.top());
+
+        minStack.pop();
+        assertThrows(EmptyStackException.class, minStack::getMin);
+    }
+
+    @Test
+    public void testIncreasingSequence() {
+        MinStackUsingTwoStacks minStack = new MinStackUsingTwoStacks();
+        minStack.push(1);
+        minStack.push(2);
         minStack.push(3);
-        minStack.push(5);
-        assertEquals(3, minStack.getMin());
+        minStack.push(4);
+
+        assertEquals(1, minStack.getMin());
+        assertEquals(4, minStack.top());
+
+        minStack.pop();
+        minStack.pop();
+        assertEquals(1, minStack.getMin());
+        assertEquals(2, minStack.top());
+    }
 
+    @Test
+    public void testDecreasingSequence() {
+        MinStackUsingTwoStacks minStack = new MinStackUsingTwoStacks();
+        minStack.push(4);
+        minStack.push(3);
         minStack.push(2);
         minStack.push(1);
+
         assertEquals(1, minStack.getMin());
+        assertEquals(1, minStack.top());
 
         minStack.pop();
         assertEquals(2, minStack.getMin());
+        assertEquals(2, minStack.top());
     }
 }

From e843dcdd96a9cef6b68a8e458d7a923c410b80de Mon Sep 17 00:00:00 2001
From: alxkm <alexanderklmn@gmail.com>
Date: Mon, 14 Jul 2025 19:59:17 +0200
Subject: [PATCH 2/2] checkstyle: fix import order

---
 .../com/thealgorithms/stacks/MinStackUsingTwoStacksTest.java    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/java/com/thealgorithms/stacks/MinStackUsingTwoStacksTest.java b/src/test/java/com/thealgorithms/stacks/MinStackUsingTwoStacksTest.java
index ec993fd2f1e0..36bdde49b235 100644
--- a/src/test/java/com/thealgorithms/stacks/MinStackUsingTwoStacksTest.java
+++ b/src/test/java/com/thealgorithms/stacks/MinStackUsingTwoStacksTest.java
@@ -3,8 +3,8 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
-import org.junit.jupiter.api.Test;
 import java.util.EmptyStackException;
+import org.junit.jupiter.api.Test;
 
 public class MinStackUsingTwoStacksTest {