Jul 17, 2025 · Jul 17, 2025
diff --git a/src/test/java/com/thealgorithms/stacks/PostfixEvaluatorTest.java b/src/test/java/com/thealgorithms/stacks/PostfixEvaluatorTest.java
 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("1 0 /"));
    }

    @Test
    @DisplayName("Should throw IllegalArgumentException for invalid characters")
    void testInvalidToken() {
        assertThrows(IllegalArgumentException.class, () -> PostfixEvaluator.evaluatePostfix("1 a +"));
    }
 }
Original file line number	Diff line number	Diff line change
Expand Up		@@ -4,24 +4,41 @@
		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("1 0 /"));
		}

		@Test
		@DisplayName("Should throw IllegalArgumentException for invalid characters")
		void testInvalidToken() {
		assertThrows(IllegalArgumentException.class, () -> PostfixEvaluator.evaluatePostfix("1 a +"));
		}
		}