Node.js Testing

Bug Detection:

Code Quality:

Enforce code quality standards and prevent regressions

Documentation:

Confidence:

Collaboration:

CI/CD:

Enable continuous integration and deployment pipelines

Unit Testing

if (typeof a !== 'number' || typeof b !== 'number') {
throw new Error('Both arguments must be numbers');
}
return a + b;
}
function subtract(a, b) {
if (typeof a !== 'number' || typeof b !== 'number') {
throw new Error('Both arguments must be numbers');
}
return a - b;
}
module.exports = { add, subtract };
test/calculator.test.js const assert = require('assert');
const { add, subtract } = require('./calculator');
// Test the add function assert.strictEqual(add(1, 2), 3, 'Addition not working correctly');
assert.strictEqual(add(-1, 1), 0, 'Addition with negative numbers not working');
// Test the subtract function assert.strictEqual(subtract(5, 2), 3, 'Subtraction not working correctly');
assert.strictEqual(subtract(2, 5), -3, 'Subtraction resulting in negative not working');
console.log('All tests passed!');

Integration Testing

const app = express();
app.get('/users', (req, res) => {
res.json([
{ id: 1, name: 'Alice' },
{ id: 2, name: 'Bob' }
]);
});
module.exports = app;
test.js const assert = require('assert');
const http = require('http');
const app = require('./app');
// Start the server const server = app.listen(8080);

http.get('http://localhost:8080/users', (res) => {
let data = '';
res.on('data', (chunk) => {
data += chunk;
});
res.on('end', () => {
const users = JSON.parse(data);
// Verify the response assert.strictEqual(res.statusCode, 200, 'Status code should be 200');
assert.strictEqual(users.length, 2, 'Should return two users');
assert.strictEqual(users[0].name, 'Alice', 'First user should be Alice');
assert.strictEqual(users[1].name, 'Bob', 'Second user should be Bob');
console.log('API test passed!');
// Close the server server.close();
});
}).on('error', (err) => {
console.error('Test failed:', err);
server.close();
});

End-to-End Testing

These tests typically use tools like

WebdriverIO

Note:

Test - Driven Development (TDD)
Test - Driven Development is a software development approach where you:

Refactor the code to meet quality standards

Repeat for each new feature or improvement

TDD Example: Developing a Password Validator password - validator.test.js

// 1. Write the test first const assert = require('assert');
const validatePassword = require('./password-validator');
// Test for password length assert.strictEqual(validatePassword('abc12'), false, 'Should reject passwords shorter than 8 characters');
assert.strictEqual(validatePassword('abcdef123'), true, 'Should accept passwords 8+ characters long');
// Test for number requirement assert.strictEqual(validatePassword('abcdefgh'), false, 'Should reject passwords without numbers');
assert.strictEqual(validatePassword('abcdefg1'), true, 'Should accept passwords with numbers');
console.log('All password validation tests passed!');

// 2. Run the test - it will fail because validatePassword doesn't exist yet password - validator.js

// 3. Write the simplest code to pass the tests function validatePassword(password) {
// Check length (at least 8 characters)
if (password.length < 8) {
return false;
}
// Check if it contains at least one number if (!/\d/.test(password)) {
return false;
}
return true;
}
module.exports = validatePassword;

// 4. Run the tests again - they should pass now

Testing Best Practices

Write Testable Code

Single Responsibility Principle:

Each function should do one thing well

Pure Functions:

Dependency Injection:

Test Organization