Test automation, hands on.

Short lessons, exercises graded in your browser and everyday reference. Your tests run against the correct code and against planted bugs: you see right away what they detect and what they let escape.

Free, no signup.

Start at level 1See the tracks

Try it: the age of majority rule

level 1 · 3 bugs

isAdult(age) returns true from age 18. The test below passes but detects no bug. Improve it and run.

Your tests

0 of 3 bugs detected

  • Bug 1: hidden
  • Bug 2: hidden
  • Bug 3: hidden

The concept and the hints are in the lesson “Both sides of a rule”.

Tracks by level

Each lesson has a concept, a rule of thumb and an exercise. Your progress stays in this browser only.

All tracks
Tracks by level, with your progress in this browser
LevelTrackProgress
1FoundationsWrite tests that catch real bugs: both sides of a rule, boundary values, one broken rule at a time, every combination of conditions and state transitions. Then report a defect that can be reproduced and turn acceptance criteria into tests.0 of 7
2PractitionerTDD with hidden checks and tests for a class with state and errors. Write the code from a list of tests, face the edge cases of money and errors, and test a class with state. Then decide the order of tests when time is short and estimate the effort with a technique.0 of 5
3AdvancedContract, visual regression, performance and test suite architecture.Planned for the next phase
4ExpertEvaluating AI features, risk-based strategy and observability.Planned for the next phase

Practice

Direct training with no theory, and free environments to experiment.

Bug Hunt

Each exercise hides bugs in a function. Write tests that pass on the correct code and catch them all. Good for warming up before an interview or reviewing a technique.

6 exercises · levels 1 and 2

Open Bug Hunt

Playgrounds

Free environments by technique, ungraded. To try an idea or show a concept to the team.

All playgrounds

Reference

To consult day to day.

Guides

Concepts and decisions, in depth.

Recipes

Code patterns ready to adapt.

Tools

When to choose each one.

This Lab is tested in public

On every release, CI runs the same discipline we teach.

See how we test

  • Unit and component tests
  • End-to-end tests in the browser
  • Accessibility in four theme modes
  • Performance budget per route
  • Exercises solved by reference answers
  • Every planted bug is detectable