@Test void testSubtract() { assertEquals(5, calculator.subtract(10, 5), "Subtraction failed"); }

public static void main(String[] args) { Calculator calculator = new Calculator(); System.out.println("Addition: " + calculator.add(10, 5)); System.out.println("Subtraction: " + calculator.subtract(10, 5)); System.out.println("Multiplication: " + calculator.multiply(10, 5)); System.out.println("Division: " + calculator.divide(10, 5)); } } 4.1 Write Unit Tests Create a test class CalculatorTest.java in src/test/java/com/example :

public double subtract(double a, double b) { return a - b; }

package com.example;

public class CalculatorTest {

public double add(double a, double b) { return a + b; }

public class App {