Continue Developing the calculateDiscount Function

Welcome to your second lesson for this course dedicated to practicing Test Driven Development (TDD) utilizing TypeScript and Jest. In this unit, we will continue adding featurs to our calculateDiscount function. We have 5 more requirements for you to implement!

In this course, emphasis is placed on hands-on practice, where you'll receive requirements through tests, one at a time. Your task is to implement code that makes each test pass, simulating a real-world TDD environment. As the course guide, it's akin to being your pair programmer, providing test-driven prompts to hone your skills as you progress.

As a reminder, the Red-Green-Refactor cycle is central to TDD, guiding your development process:

• Red: Start by writing a failing test to define the next step.
• Green: Implement just enough code to pass the test, focusing on functionality.
• Refactor: Optimize the code for clarity and efficiency without changing its behavior.

• Description: The function should validate that the price is a numeric value and throw an error if a non-numeric input is provided.
• Test Case:
  TypeScript

  it('should throw an error for non-numeric price inputs', () => {
    // Arrange
    const originalPrice = 'invalid' as any;
    const discountPercentage = 10;
  
    // Act, Assert
    expect(() => calculateDiscount(originalPrice, discountPercentage)).toThrow('Price must be a valid number');
  });

• Description: The function should validate that the discount percentage is a numeric value and throw an error if a non-numeric input is provided.
• Test Case:
  it('should throw an error for non-numeric discount inputs', () => {
    // Arrange
    const originalPrice = 100;
    const discountPercentage = 'invalid' as any;
    
    // Act, Assert
    expect(() => calculateDiscount(originalPrice, discountPercentage)).toThrow('Discount must be a valid number');
  });