
Description: Mockup.io is a web-based wireframing and mockup tool that allows users to quickly create wireframes, prototypes, and mockups for web and mobile apps. It has a simple and intuitive drag-and-drop interface with hundreds of UI elements and templates to choose from.
Type: Open Source Test Automation Framework
Founded: 2011
Primary Use: Mobile app testing automation
Supported Platforms: iOS, Android, Windows

Description: Principle is an open-source visual tool for building interactive UIs. It allows designers and developers to design, prototype, animate and develop user interfaces without writing code. Principle focuses on animations and interactions.
Type: Cloud-based Test Automation Platform
Founded: 2015
Primary Use: Web, mobile, and API testing
Supported Platforms: Web, iOS, Android, API