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Testing

Writing tests that actually catch bugs. Unit, integration, and end-to-end.

Browse 38 tutorials → Other topics

Why learn Testing?

  • Tests turn fear into a green checkmark before every deploy.

  • A small testing habit pays back compounding interest.

  • Engineers who test ship faster, not slower, over the long run.

  • A near-universal expectation for senior roles.

What you can build with Testing

Pytest, Vitest, Jest, Playwright Catching regressions in CI Refactoring with confidence Documenting expected behavior

Testing tutorials

38 articles · page 1 of 2

Hand-written tutorials, ordered as a recommended learning path.

  1. 01 What Is Testing? An honest introduction to automated testing — unit, integration, and end-to-end tests, the testing pyramid, why tests pay back over time, and common excuses for skipping them.
  2. 02 Pytest Basics A practical introduction to pytest — installation, test discovery, the assert statement, parametrize, fixtures, and the command-line flags you will use every day.
  3. 03 Vitest Basics A practical introduction to Vitest — why it exists, installation, describe and it, expect matchers, watch mode, and a small mock example for testing modern JavaScript.
  4. 04 Mocks & Stubs The test-double vocabulary cleared up — mocks vs stubs vs fakes vs spies, when to mock at boundaries, when over-mocking ruins tests, with Python and JavaScript examples.
  5. 05 Chaos Engineering Learn chaos engineering principles and tools. Run controlled experiments with Chaos Monkey, Litmus, and Gremlin to find weaknesses before they cause real outages.
  6. 06 Integration Testing Learn how to write effective integration tests that verify real database queries, API calls, and service interactions using testcontainers and proper test infrastructure.
  7. 07 Performance Testing Learn load testing, stress testing, and spike testing with k6 and Locust. Includes test scripts, result interpretation, and strategies for finding bottlenecks.
  8. 08 TDD Guide Learn the TDD workflow with real examples in Python and JavaScript. Covers red-green-refactor, when TDD works best, and how to handle common challenges.
  9. 09 Jest vs Vitest Compare Jest and Vitest for JavaScript testing. Understand speed, configuration, compatibility, and migration tradeoffs to pick the right test runner.
  10. 10 WCAG Auditing Audit your site for WCAG 2.2 compliance using automated tools, manual testing checklists, and CI integration. Covers axe-core, Lighthouse, screen reader testing, and remediation.
  11. 11 Contract Testing (Pact) Learn how Pact contract testing catches integration bugs between microservices without needing a full end-to-end environment.
  12. 12 API Testing (Supertest) Learn how to write fast, reliable API tests for Express and Node.js backends using Supertest and Jest.
  13. 13 Chaos Engineering Learn chaos engineering fundamentals and run your first experiments to build confidence in your system's resilience.
  14. 14 Load Testing (k6) Learn how to write and run load tests with k6 to find performance bottlenecks before your users do.
  15. 15 Mutation Testing Learn how mutation testing works, why code coverage alone is misleading, and how to use tools like Stryker and mutmut to find weak tests.
  16. 16 Property-Based Testing Learn property-based testing with Hypothesis to find edge cases your example-based tests miss and write more robust Python code.
  17. 17 Snapshot Testing Learn when snapshot tests help, when they hurt, and how to use them effectively in React, API, and configuration testing.
  18. 18 TDD Workflow Walk through the red-green-refactor cycle step by step, building a password validator to learn practical test-driven development.
  19. 19 Test Doubles Understand the differences between test doubles: mocks, stubs, spies, and fakes, with practical examples in JavaScript and Python.
  20. 20 Visual Regression Catch unintended UI changes automatically by comparing screenshots with Playwright's built-in visual comparison tools.