Workflowy is a simple, focused bullet-list tool. As a Test Engineer, it's a flexible notebook for organizing work. It minimizes distraction, allowing quick structuring of test cases, plans, and exploratory notes.

Free & OpenSource REST API Testing Tool for all levels in a Test Pyramid

Built for developers and testers alike, SoapUI is the only open source tool that covers the entire testing spectrum (functional, security, load, mocking).

Bruno is a Fast and Git-Friendly Opensource API client, aimed at revolutionizing the status quo represented by Postman, Insomnia and similar tools out there.

Jupyter Notebook is an interactive, browser-based environment for running code alongside notes, results, and visualisations, making it useful for exploration, analysis, and sharing reproducible work.

Gatling is a powerful open-source load testing solution that integrates with your development pipeline. It includes a web recorder and colorful reports.