**Course Title:** Testing Frameworks: Principles and Practices **Section Title:** Test-Driven Development (TDD) and Behavior-Driven Development (BDD) **Topic:** Practice TDD by developing a feature from scratch using test cases. (Lab topic) **Introduction** In this lab, you'll apply the principles of Test-Driven Development (TDD) to develop a new feature from scratch. You'll write test cases first, then implement the feature, and finally, refactor your code to make it more efficient. This hands-on experience will help you understand the benefits and challenges of TDD and how to integrate it into your development workflow. **Prerequisites** Before starting this lab, make sure you have: 1. Basic knowledge of a programming language (e.g., JavaScript, Python, or Java). 2. Familiarity with a testing framework (e.g., Jest, Mocha, JUnit, or NUnit). 3. A code editor or IDE (Integrated Development Environment) of your choice. **Lab Objective** Develop a simple calculator feature using TDD. The calculator should have methods for basic arithmetic operations (addition, subtraction, multiplication, and division). **Step 1: Set up your project and testing framework** 1. Create a new project folder and initialize it with a package manager (e.g., npm or pip). 2. Install a testing framework of your choice (e.g., Jest or Mocha for JavaScript, or JUnit for Java). 3. Create a new test file for your calculator feature (e.g., `calculator.test.js`). **Step 2: Write your first test case** 1. Define a test case for the `add` method of your calculator. 2. Use a testing framework to write a test function that takes two numbers as inputs and verifies the correct output (e.g., `test('add 2 + 2', () => { ... });`). 3. Use an assertion library (e.g., `expect` in Jest or Mocha, or `org.junit` in JUnit) to verify the expected result. Example: ```javascript // using Jest test('add 2 + 2', () => { const calculator = new Calculator(); expect(calculator.add(2, 2)).toBe(4); }); ``` **Step 3: Run your test case and see it fail** 1. Run your test case using your testing framework (e.g., `jest` or `mocha`). 2. Observe the test failure due to the missing `Calculator` class and `add` method. **Step 4: Implement the calculator feature** 1. Create a new file for your `Calculator` class (e.g., `calculator.js`). 2. Implement the `add` method to perform the basic arithmetic operation. Example: ```javascript class Calculator { add(a, b) { return a + b; } } ``` **Step 5: Run your test case and see it pass** 1. Run your test case again using your testing framework. 2. Observe the test pass, indicating that your `add` method works correctly. **Step 6: Refactor your code** 1. Refactor your `Calculator` class to make it more efficient or readable. Example: ```javascript class Calculator { add(...args) { return args.reduce((a, b) => a + b, 0); } } ``` **Step 7: Repeat the process for other methods** 1. Repeat steps 2-6 for other arithmetic operations (subtraction, multiplication, and division). 2. Write test cases for each method before implementing them. **Conclusion** You've successfully applied the principles of TDD to develop a calculator feature from scratch. By writing test cases first, you've ensured that your code is testable and maintainable. **Practical Takeaways** 1. TDD helps ensure that your code is testable and maintainable. 2. Write test cases before implementing features to ensure correct functionality. 3. Refactor your code to make it more efficient and readable. **Additional Resources** * [Jest Documentation](https://jestjs.io/docs/en/getting-started) * [Mocha Documentation](https://mochajs.org/#getting-started) * [JUnit Documentation](https://junit.org/junit5/docs/current/user-guide/#writing-tests) **Leave a Comment or Ask for Help** If you have any questions or need help with this lab, please leave a comment below. **What's Next?** In the next topic, we'll cover "Understanding performance testing: Load, stress, and endurance testing." from the Performance Testing section.