Why testing matters in Node.js - See It in Action

Why Testing Matters in Node.js

📖 Scenario: You are building a simple Node.js module that calculates the total price of items in a shopping cart. To make sure your code works correctly and keeps working as you add features, you will write tests.

🎯 Goal: Build a Node.js module with a function to sum item prices and write a basic test to check it works correctly.

📋 What You'll Learn

Create a list of item prices as numbers

Create a variable to hold the total price starting at 0

Write a function that sums all prices in the list

Write a simple test using Node.js assert to check the function output

💡 Why This Matters

🌍 Real World

Testing helps catch mistakes early and keeps your code working as you add new features, just like checking your work in school before submitting.

💼 Career

Writing tests is a key skill for software developers to ensure code quality and reliability in real projects.

1

Create the list of item prices

Create a variable called prices and set it to an array with these exact numbers: 10, 20, 30

Node.js

// Create the prices array
// Your code here

Need a hint?

Use const to create an array named prices with the numbers 10, 20, and 30 inside square brackets.

2

Create a variable to hold the total price

Create a variable called total and set it to 0 to start counting the sum of prices

Node.js

const prices = [10, 20, 30];
// Create a total variable set to 0
// Your code here

Need a hint?

Use let to create a variable named total and set it to 0.

3

Write a function to sum all prices

Write a function called calculateTotal that takes the prices array and returns the sum of all prices using a for loop with price as the iterator variable

Node.js

const prices = [10, 20, 30];
let total = 0;
// Write calculateTotal function here
// Your code here

Need a hint?

Define a function named calculateTotal that loops over prices using for (const price of prices) and adds each price to a sum variable, then returns sum.

4

Write a simple test to check the function

Import Node.js assert module and write a test using assert.strictEqual to check that calculateTotal(prices) equals 60

Node.js

const prices = [10, 20, 30];
let total = 0;
function calculateTotal(prices) {
    let sum = 0;
    for (const price of prices) {
        sum += price;
    }
    return sum;
}
// Import assert and write test below
// Your code here

Need a hint?

Use import assert from 'assert' at the top and then write assert.strictEqual(calculateTotal(prices), 60) to check the function returns 60.