From ef82cad5d648f40023eca44314e927edf4164026 Mon Sep 17 00:00:00 2001
From: alxkm <alexanderklmn@gmail.com>
Date: Thu, 17 Jul 2025 22:53:22 +0200
Subject: [PATCH 1/2] testing: improving PostfixEvaluatorTest

---
 .../stacks/PostfixEvaluatorTest.java          | 37 +++++++++++++++----
 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/src/test/java/com/thealgorithms/stacks/PostfixEvaluatorTest.java b/src/test/java/com/thealgorithms/stacks/PostfixEvaluatorTest.java
index 882fe644ccd5..8afd8617239c 100644
--- a/src/test/java/com/thealgorithms/stacks/PostfixEvaluatorTest.java
+++ b/src/test/java/com/thealgorithms/stacks/PostfixEvaluatorTest.java
@@ -4,24 +4,47 @@
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.util.EmptyStackException;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
 
 public class PostfixEvaluatorTest {
 
-    @Test
-    public void testValidExpressions() {
-        assertEquals(22, PostfixEvaluator.evaluatePostfix("5 6 + 2 *"));
-        assertEquals(27, PostfixEvaluator.evaluatePostfix("7 2 + 3 *"));
-        assertEquals(3, PostfixEvaluator.evaluatePostfix("10 5 / 1 +"));
+    @ParameterizedTest(name = "Expression: \"{0}\" → Result: {1}")
+    @CsvSource({"'5 6 + 2 *', 22", "'7 2 + 3 *', 27", "'10 5 / 1 +', 3", "'8', 8", "'3 4 +', 7"})
+    @DisplayName("Valid postfix expressions")
+    void testValidExpressions(String expression, int expected) {
+        assertEquals(expected, PostfixEvaluator.evaluatePostfix(expression));
     }
 
     @Test
-    public void testInvalidExpression() {
+    @DisplayName("Should throw EmptyStackException for incomplete expression")
+    void testInvalidExpression() {
         assertThrows(EmptyStackException.class, () -> PostfixEvaluator.evaluatePostfix("5 +"));
     }
 
     @Test
-    public void testMoreThanOneStackSizeAfterEvaluation() {
+    @DisplayName("Should throw IllegalArgumentException for extra operands")
+    void testExtraOperands() {
         assertThrows(IllegalArgumentException.class, () -> PostfixEvaluator.evaluatePostfix("5 6 + 2 * 3"));
     }
+
+    @Test
+    @DisplayName("Should throw ArithmeticException for division by zero")
+    void testDivisionByZero() {
+        assertThrows(ArithmeticException.class, () -> PostfixEvaluator.evaluatePostfix("5 0 /"));
+    }
+
+    @Test
+    @DisplayName("Should throw IllegalArgumentException for invalid characters")
+    void testInvalidToken() {
+        assertThrows(IllegalArgumentException.class, () -> PostfixEvaluator.evaluatePostfix("5 a +"));
+    }
+
+    @Test
+    @DisplayName("Should throw EmptyStackException for empty input")
+    void testEmptyInput() {
+        assertThrows(EmptyStackException.class, () -> PostfixEvaluator.evaluatePostfix(""));
+    }
 }

From bc2d6b95b3ba8211c441b690c6e7d6dffcbb79d0 Mon Sep 17 00:00:00 2001
From: alxkm <alexanderklmn@gmail.com>
Date: Thu, 17 Jul 2025 22:57:28 +0200
Subject: [PATCH 2/2] testing: redundant cases

---
 .../com/thealgorithms/stacks/PostfixEvaluatorTest.java | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/src/test/java/com/thealgorithms/stacks/PostfixEvaluatorTest.java b/src/test/java/com/thealgorithms/stacks/PostfixEvaluatorTest.java
index 8afd8617239c..682240acd752 100644
--- a/src/test/java/com/thealgorithms/stacks/PostfixEvaluatorTest.java
+++ b/src/test/java/com/thealgorithms/stacks/PostfixEvaluatorTest.java
@@ -33,18 +33,12 @@ void testExtraOperands() {
     @Test
     @DisplayName("Should throw ArithmeticException for division by zero")
     void testDivisionByZero() {
-        assertThrows(ArithmeticException.class, () -> PostfixEvaluator.evaluatePostfix("5 0 /"));
+        assertThrows(ArithmeticException.class, () -> PostfixEvaluator.evaluatePostfix("1 0 /"));
     }
 
     @Test
     @DisplayName("Should throw IllegalArgumentException for invalid characters")
     void testInvalidToken() {
-        assertThrows(IllegalArgumentException.class, () -> PostfixEvaluator.evaluatePostfix("5 a +"));
-    }
-
-    @Test
-    @DisplayName("Should throw EmptyStackException for empty input")
-    void testEmptyInput() {
-        assertThrows(EmptyStackException.class, () -> PostfixEvaluator.evaluatePostfix(""));
+        assertThrows(IllegalArgumentException.class, () -> PostfixEvaluator.evaluatePostfix("1 a +"));
     }
 }

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