Testing Playground is a Chrome extension that serves as a simple and complete DOM testing playground. Developed by Stephan, this free add-on falls under the category of Browsers and specifically the subcategory of Add-ons & Tools.

The extension adds a new tab called " Testing Playground" to the Chrome Developer Tools, as well as a side panel under the "Elements" tab. Its main purpose is to help developers find the best queries for selecting elements when using the open-source Testing-Library family.

With Testing Playground, you can easily inspect element hierarchies in the Chrome Developer Tools and receive suggestions on how to select them. The extension encourages good testing practices by providing feedback on the queries you use and suggesting better alternatives.

When you select an element on a page, Testing Playground displays the different queries that can be used to select that element in your tests. It also notifies you when there are better queries available and explains why they are better.

Overall, Testing Playground is a valuable tool for developers who want to improve their DOM testing practices. It offers a user-friendly interface within the Chrome Developer Tools and provides helpful suggestions for selecting elements in your tests.