
Description: Mattermost is an open-source, self-hosted online chat service with file sharing, search and integration capabilities. It supports text, images, videos and custom emojis across PCs and phones with instant notifications.
Type: Open Source Test Automation Framework
Founded: 2011
Primary Use: Mobile app testing automation
Supported Platforms: iOS, Android, Windows

Description: A-Chat.org is a free and open source chat server and web client that allows real-time messaging and conversations. It supports group chats, direct messaging, emoji reactions, media sharing, and more.
Type: Cloud-based Test Automation Platform
Founded: 2015
Primary Use: Web, mobile, and API testing
Supported Platforms: Web, iOS, Android, API