Continue Developing the calculateDiscount Function with Kotlin

Welcome to your second lesson, which continues to delve into Test Driven Development (TDD) practices using Kotlin and JUnit. In this unit, we will extend the functionality of our calculateDiscount function by implementing five new requirements.

Building on the previous unit, this course emphasizes practical experience by sequentially providing requirements through tests. Your mission is to implement code that satisfies each test, mirroring a real-world TDD scenario. Consider this guide your pair programmer, offering test-driven prompts to enhance your expertise incrementally.

As a reminder, the Red-Green-Refactor cycle is crucial in TDD, steering your development process:

• Red: Begin by writing a failing test to define what to do next.
• Green: Develop just enough code to pass the test, concentrating on meeting the functionality.
• Refactor: Enhance the code for clarity and efficiency without changing its behavior.

Below, you'll find additional requirements and tests designed to handle edge cases, such as negative discount percentages and capping maximum discounts. These enhancements aim to ensure the calculateDiscount function remains robust and reliable under various conditions.

• Description: The function should not accept negative discount percentages and must throw an error in such cases.
• Test Case:

import kotlin.test.Test
import kotlin.test.assertFailsWith

class DiscountCalculatorTest {
    @Test
    fun shouldThrowExceptionForDiscountsLessThanZeroPercent() {
        // Arrange
        val discountCalculator = DiscountCalculator()
        val originalPrice = 100.0
        val discountPercentage = -10.0

        // Act & Assert
        val exception = assertFailsWith<IllegalArgumentException> {
            discountCalculator.calculateDiscount(originalPrice, discountPercentage)
        }
        assert(exception.message == "Discount cannot be negative")
    }
}

This test ensures that the function throws an exception when a negative discount percentage is provided.