In 2012 Mehdi Khalili and Michael Whelan started TestStack with BDDfy, a simple yet powerful and extensible BDD framework for .Net. that Mehdi had created, and Seleno, another .Net framework for automated UI testing with Selenium. Since then, they have been joined by Krzysztof Kozmic, Jake Ginnivan and Rob Moore and the White, Fluent MVC Testing, and Convention Tests projects have been added.
The goal of TestStack is to provide frameworks that support agile teams of developers, testers, and customers develop software in a "test first" approach (aligning with the left side of Marick's Quadrant). These tests promote the "testing as design" mindset, and tend to be automated. Things like unit and integration tests, acceptance tests, and UI tests and methodologies like Behaviour Driven Development and Acceptance Test Driven Development.