How do I test CommonJS modules in Node.js?

How do I test CommonJS modules in Node.js?

You can use testing frameworks like Mocha or Jest to test CommonJS modules. Would you like a code example?

Yes, please provide a code example using Mocha.

Sure! Here's a simple example:

// myModule.js
function add(a, b) {
    return a + b;
}
module.exports = add;

// test.js
const assert = require('assert');
const add = require('./myModule');

describe('Add Function', function() {
    it('should return 5 when adding 2 and 3', function() {
        assert.strictEqual(add(2, 3), 5);
    });
});

Run the test with mocha test.js. Do you need help with anything else?

What if I want to test asynchronous functions?

For asynchronous functions, you can use the done callback or return a promise. Here's an example:

// asyncModule.js
function fetchData(callback) {
    setTimeout(() => {
        callback('data');
    }, 1000);
}
module.exports = fetchData;

// asyncTest.js
const assert = require('assert');
const fetchData = require('./asyncModule');

describe('Fetch Data Function', function() {
    it('should return data after 1 second', function(done) {
        fetchData(function(data) {
            assert.strictEqual(data, 'data');
            done();
        });
    });
});

This way, you can test asynchronous code effectively!