Smoke Testing — Explained with Examples

In this tutorial, you'll learn about Smoke Testing. We cover key concepts, practical examples, and best practices.

Smoke testing is a quick sanity check performed after a deployment to verify that the most critical functions of an application work before deeper testing.

Smoke testing (also called sanity testing or build verification testing) runs a minimal set of tests to confirm the application starts, responds to requests, and performs its primary functions. It's the first gate in the deployment pipeline.

When to Run Smoke Tests

Smoke tests run after every deployment — before the full test suite starts. If smoke tests fail, the build is rejected immediately, saving time and resources.

Code commit → Build → Deploy → Smoke Tests → Full Tests → Release
                                  ↓ fail
                              Reject build

Example: Smoke Test Suite

const axios = require('axios');

const BASE_URL = process.env.BASE_URL || 'https://staging.example.com';

describe('Smoke Tests', () => {
  test('application responds with 200', async () => {
    const response = await axios.get(BASE_URL);
    expect(response.status).toBe(200);
  });

  test('login page loads', async () => {
    const response = await axios.get(`${BASE_URL}/login`);
    expect(response.status).toBe(200);
    expect(response.data).toContain('Login');
  });

  test('API health endpoint returns healthy', async () => {
    const response = await axios.get(`${BASE_URL}/api/health`);
    expect(response.status).toBe(200);
    expect(response.data.status).toBe('healthy');
  });

  test('database connection is alive', async () => {
    const response = await axios.get(`${BASE_URL}/api/health/db`);
    expect(response.data.dbConnected).toBe(true);
  });

  test('static assets are served', async () => {
    const response = await axios.get(`${BASE_URL}/app.js`);
    expect(response.status).toBe(200);
    expect(response.headers['content-type']).toContain('javascript');
  });
});

Real-World Analogy

Smoke testing comes from hardware engineering. When you first power on a circuit board, you check if any components smoke (indicating a short circuit or wrong connection). If smoke appears, you don't bother with detailed testing — you fix the fundamental problem first. The smoke test catches catastrophic failures early.

Smoke vs Regression

Related Terms

Regression Testing, E2E Testing, Integration Testing, Unit Testing, CI/CD