About Fun UI Playground

Who builds Fun UI Playground, what the site is for, how its challenges are designed, and the conventions every page follows.

Fun UI Playground hosts 39 themed UI test automation challenges across six categories and 5 bug-hunt pages, each hiding an exactly-stated number of planted bugs. It is free, needs no signup and stores nothing server-side.

Who builds it

The site is built and maintained by Azmi Yüksel, a test automation engineer. It is one of three sibling playgrounds: funapi.dev covers mock REST APIs and fundata.dev generates synthetic test data.

Why a practice site needs rules

Every challenge follows four rules — semantic HTML first, a stable id and data-testid on every interactive element, one site-wide flash convention for outcomes, and deterministic data — so a test that fails here fails for a reason worth learning from. Exceptions exist and each says so on its own page: Challenging DOM regenerates its ids on purpose, and two pages randomise their content on purpose.

How it is built

A React single-page app on Firebase Hosting, with a small stateless backend under /api for the exercises that need real HTTP behavior: Basic and Digest Auth, arbitrary status codes, a tunable response delay, a real rate limiter, attachment downloads and an upload echo. Nothing is stored server-side. Practice progress lives in your browser; signing in is optional and only syncs it across devices.

Read next

• Getting started guide
• Glossary
• Framework comparison
• Changelog
• Privacy and data use

Updated 2026-09-07

Fun UI Playground — all challenges, bug hunts, getting started, glossary, about.