Writing test cases in Node.js - Mini Project: Build & Apply

Writing Test Cases in Node.js

📖 Scenario: You are building a simple calculator module in Node.js. To make sure your calculator works correctly, you need to write test cases that check its functions.

🎯 Goal: Create a test file using Node.js and the built-in assert module to write test cases for a calculator module with add and subtract functions.

📋 What You'll Learn

Create a calculator object with add and subtract functions

Create a variable called testCases to hold test descriptions and expected results

Write test cases using assert.strictEqual to check the calculator functions

Add a final line to run all test cases and show success or failure

💡 Why This Matters

🌍 Real World

Writing test cases helps catch bugs early and ensures your code works as expected before sharing or deploying it.

💼 Career

Testing is a key skill for software developers to maintain code quality and reliability in professional projects.

1

Create the calculator object

Create a constant called calculator that is an object with two functions: add and subtract. Each function takes two parameters a and b and returns their sum or difference respectively.

Node.js

// Create the calculator object with add and subtract functions
// Your code here

Need a hint?

Use an object literal with arrow functions for add and subtract.

2

Create test cases array

Create a constant called testCases that is an array of objects. Each object should have description, func, args, and expected properties. Add two test cases: one for add(2, 3) expecting 5, and one for subtract(5, 2) expecting 3.

Node.js

const calculator = {
  add: (a, b) => a + b,
  subtract: (a, b) => a - b
};

// Create the testCases array with two test objects
// Your code here

Need a hint?

Each test case is an object describing the test and expected result.

3

Write test runner with assertions

Import the built-in assert module with const assert = require('assert');. Then write a for loop that goes through each object in testCases. Inside the loop, use assert.strictEqual to check that calling func with args equals expected. Use the description as the message for the assertion.

Node.js

const calculator = {
  add: (a, b) => a + b,
  subtract: (a, b) => a - b
};

const testCases = [
  { description: 'add 2 + 3', func: calculator.add, args: [2, 3], expected: 5 },
  { description: 'subtract 5 - 2', func: calculator.subtract, args: [5, 2], expected: 3 }
];

// Import assert and write a for loop to run tests
// Your code here

Need a hint?

Use destructuring in the for loop and spread args when calling func.

4

Add final success message

After the for loop, add a line that logs 'All tests passed!' to the console.

Node.js

const assert = require('assert');

const calculator = {
  add: (a, b) => a + b,
  subtract: (a, b) => a - b
};

const testCases = [
  { description: 'add 2 + 3', func: calculator.add, args: [2, 3], expected: 5 },
  { description: 'subtract 5 - 2', func: calculator.subtract, args: [5, 2], expected: 3 }
];

for (const { description, func, args, expected } of testCases) {
  assert.strictEqual(func(...args), expected, description);
}

// Add console log for success message
// Your code here

Need a hint?

This message shows when all assertions succeed.