From About Us page:
What happens in a typical Weekend Testing session
Testers register for the coming weekend testing session at least a day in advance, by sending an email. A facilitator for the session provides a link to the product to be tested ( typically open source ), creates a group chat and a mission to achieve by the end of one hour testing session. The mission could vary from finding functional issues to exploring testability to writing automated tests to investigating bug reports and so on …
At the end of one hour ( or the decided session end time ) testers start sharing their experiences, bugs, learning, challenges, questions, and so on for about an hour. The facilitator then takes a day or two to prepare an experience report and publishes on this portal for the public to view it and also sends it to the open source developers or project owners for their perusal.
2 hours in total – that’s it. Every minute – worth it.